Muscular Dystrophy

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Continuing Education Activity

The term "muscular dystrophy" incorporates an assortment of hereditary disorders that lead to progressive, generalized disease of the muscle prompted by inadequate or missing glycoproteins in the muscle cell plasma membrane. This activity outlines the evaluation and treatment of muscular dystrophy and highlights the role of the healthcare team in managing patients with this condition.

Objectives:

  • Identify the etiological related to muscular dystrophy.
  • Review the evaluation and functional assessment of various muscular dystrophies.
  • Outline the available management alternatives for muscle dystrophy.
  • Summarize interprofessional team strategies for improving care coordination and communication to improve outcomes for patients affected by muscular dystrophy.

Introduction

General Information

The term "muscular dystrophy" incorporates an assortment of hereditary disorders that lead to progressive, generalized disease of the muscle prompted by inadequate or missing glycoproteins in the muscle cell plasma membrane.[1] Muscular dystrophy is a non-communicable disorder with abundant variations.[2] Each has its pattern of inheritance, onset period, and the rate at which muscle is lost.[2] Alterations in specific genes cause different representations of this disease.

Anatomy 

Research has established that the gracilis, semimembranosus, semitendinosus, and sartorius muscles can be affected in patients with muscular dystrophy.[3] Feet can exhibit an equinovarus deformity.[4] The pelvis can tilt.[5] There may be contractures throughout the body.[6] Spinal deformities may produce lordosis or scoliosis.[7] The eye can exhibit cataracts and bilateral ptosis.[8]

Natural History

Onset usually occurs in the third to fourth decades.[9] But, it may reveal in infancy or undergo accelerated deterioration near the age of onset.[10] Parents of affected individuals may present concern that their child is not walking as well as other children their age.[11][12] The child may have trouble kicking a ball due to weakness.[13] Pseudo-drop events caused by weakness of quadriceps muscle may also be present.[5] Both parents could be healthy.[14] On physical examination, the affected individual will have massive calf muscles plus lower limb proximal muscle weakness.[15] This condition will make affected individuals want to utilize their arms and hands to aid in rising from a seated position.[16] Other complaints can involve a history of delayed ambulation, toe walking, calf hypertrophy, and proximal hip girdle muscle instability.[17] 

Presentations may also incorporate asymptomatic elevation of serum creatine kinase (CK), exertion intolerance, dilated cardiomyopathy, malignant hyperthermia, quadriceps myopathy, language delay, and Turner syndrome (Duchenne in X chromosome monozygotic females).[18] For some with subclinical muscular dystrophy, the diagnosis is initially suspected by family history or the appearance of raised liver enzymes, the basis for which is unclear.[19] These enzymes may include alanine aminotransferase and aspartate aminotransferase.[19] 

Since the inheritance of muscular dystrophy can be X-linked, the overwhelming majority of patients are male.[20] Symptomatic disease in daughters is explainable by Turner syndrome, skewed X chromosome inactivation, translocation of the mutated gene to an autosome, or uniparental disomy (both copies of a chromosome set originated of one parent).[21] Usually, symptomatic females present in infancy with proximal muscle weakness.[22] Reports exist of increased weakness in adulthood, myalgias, spasms, and lethargy as initial manifestations.[15] Scoliosis and sustained alveolar hypoventilation can cause severe problems for every child with muscular dystrophy.[23]

Patterns of Spread

Muscular dystrophy can be caused by mutations in numerous genes and can be transferred in an X-linked, autosomal dominant, or autosomal recessive fashion.[24] Changes in the X-linked gene DMD, which encodes dystrophin, is the most frequent cause of muscular dystrophy.[20] This why the phenotype is manifested in hemizygous males because they have only a single copy of the X chromosome.[25] One should note that mutations in dystrophin also create allelic heterogeneity.[26] Mutations in the DMD gene, for example, may cause muscular dystrophy of both Duchenne or the less serious Becker, based on the extent of the lack of protein.[27] 

Although the phenotypic characteristics of some of these disorders are definite, the phenotypic spectrum produced by mutations in various genes overlaps, whereby spanning to nonallelic heterogeneity.[28] Identification of nonallelic heterogeneity is critical for specific reasons: (1) the capacity to recognize disease loci in linkage studies is decreased by introducing subjects with associated phenotypes, but separate genetic disorders[29]; (2) genetic testing is further complicated because several distinct genes need to be analyzed along with the likelihood of distinctive mutations in all of the candidate genes[29]; and (3) data is concerned about how genes or proteins associate, therefore providing novel insights inside cell molecular physiology.[29] 

Phenocopies are thus produced, which are incidents in which nongenetic diseases simulate a genetic disorder. [30] For instance, features of virus or toxin-induced neurologic symptoms can mirror those seen in muscular dystrophy. As in nonallelic heterogeneity, phenocopies continue to confound linkage studies and genetic testing.[30] Patient history and accurate differentiation in phenotype can usually render signs that differentiate these maladies from similar genetic diseases. It is important to note that muscular dystrophy has variable expressivity and incomplete penetrance and, therefore, may be combined over a phenotypic spectrum in various affected individuals, further demonstrating the aspect of variable expressivity.[31]  

Etiology

Cause  

Muscular dystrophy most often results from defective or absent glycoproteins in the muscle membrane.[1] Each type of muscular dystrophy results from different gene deletions or mutations, causing various enzymatic or metabolic defects. [32] The dystrophin gene is the largest in the human genome, with 79 exons.[33] The dystrophin gene is subject to a high rate of spontaneous mutations because of its enormous size (>2 × 106 bases).[34]

Effect

Modes of Inheritance  

  • Autosomal Dominant, Autosomal Recessive, X-Linked: Emery-Dreifuss (EDMD)
  • Autosomal Dominant, Autosomal Recessive: Limb-Girdle (Dysferlinopathy, Erb), Pelvifemoral, Scapulohumeral
  • Autosomal Dominant: Facioscapulohumeral (Landouzy-Dejerine), Late-Onset Distal (>40 Years old), Myotonic, Oculopharyngeal, Scapuloperoneal
  • Autosomal Recessive: Congenital, Early Onset Distal (<40 years old)
  • X-Linked: Becker (Benign Pseudohypertrophic), Duchenne (pseudohypertrophic)

Autosomal Dominant, Autosomal Recessive, X-Linked Inheritance

  • Emery-Dreifuss (EDMD)

Emery-Dreifuss Muscular Dystrophy: Caused by an X-linked recessive defect in nuclear protein emerin at the Xq27-28 position.[35] This variant can also result from an autosomal recessive or autosomal dominant defect in inner nuclear lamina proteins lamin A/C on chromosome 1.[36]

Autosomal Dominant, Autosomal Recessive Inheritance

  • Limb-Girdle (Erb)
  • Pelvifemoral *
  • Scapulohumeral *

Limb-Girdle (Erb) Muscular Dystrophy: The majority are autosomal recessive but can be autosomal dominant.[37] The age of onset is variable with the distribution of involved muscles to include limbs and trunk. May display a heterogeneous phenotype.[37] The recessive form of the disease tends to have an earlier onset and progresses more quickly, whereas the dominant form follows a slower and more variable course.[24] Several different genes have been implicated in this disease—this type of muscular dystrophy correlates with deficiencies identified in multiple proteins. Sarcoglycan, calpain, dystroglycan, and dysferlin may be most common.[38] Also may involve telethonin, lamin A/C, myotilin, and caveolin-3.[39] LGMB 1A: is caused by myotilin gene deletion.[40] 

LGMB 1B results from by lamin A/C gene deletion.[41] LGMD 1C is the result of a caveolin 3 gene deletion.[42] A calpain gene mutation causes LGMD 2A.[43] LGMD 2B is caused by dysferlin gene deletion.[44] LGMD 2C is caused by sarcoglycan gene deletion.[45] LGMD 2D is caused by sarcoglycan gene deletion.[46] LGMD 2E is caused by sarcoglycan gene deletion.[47] LGMD 2F is caused by sarcoglycan gene deletion.[48] LGMD 2G results from telethonin gene mutation.[49] LGMD 2H is caused by a TRIM32 (tripartite motif-containing) gene 32 mutation.[50] LGMD 2I is the result of a fukutin-related protein gene deletion.[51]

Autosomal Dominant Inheritance

  • Facioscapulohumeral (Landouzy-Dejerine)
  • Late-Onset Distal (>40 Years old) *
  • Myotonic
  • Oculopharyngeal
  • Scapuloperoneal *

Facioscapulohumeral (FSHD) Muscular Dystrophy: Caused by an autosomal dominant deletion of 3.3 kb repeat on chromosome 4.[52] Approximately 95% of cases are due to a mutation in the D4Z4 region in FSHD1.[53] Other areas, such as the SMCHD1 region in FSHD2, can also cause this disease.[54] The age of onset is approximately 10 to 30 years old, with the distribution of affected muscles involved to be face, neck, and shoulders.[53]

Myotonic Muscular Dystrophy: Myotonic muscular dystrophy (or simply Myotonic dystrophy) results from the impaired expression of the Dystrophia Myotonica Protein Kinase (DMPK).[55] Caused by an autosomal dominant abnormally expanded CTG trinucleotide repeat sequence located in the 3′ untranslated region of the Dystrophia Myotonica Protein Kinase (DMPK) gene.[56] Because this mechanism involves the expansion of trinucleotide repeat sequences (CTG), the phenomenon of amplification and anticipation occurs (i.e., family members get the disease at earlier and earlier ages throughout the generations).[57] 

Clinical severity increases as the number of nucleotide repeats increases; some cases can be in the thousands.[58] Age of onset is approximately 10 to 15 years old with the distribution of involved muscles to include face and extremities. Some cases can be in the thousands.[58] This defect is classically associated with chromosome 19; however, a second form can occur on chromosome 3q.[10][59]

Oculopharyngeal Muscular Dystrophy: Age of onset is approximately 30 to 40 years of age. Distribution of involved muscles includes the extraocular and pharyngeal muscles. Caused by an autosomal dominant GCG trinucleotide repeat resulting in deficient mRNA transfer from the nucleus.[60]

Autosomal Recessive Inheritance

  • Congenital
  • Early Onset Distal (<40 years old) *

Congenital Muscular Dystrophy: Caused by a mutation of the sarcolemmal protein Merosin gene, deficiencies or mutations in laminin-alpha 2, collagen type VI, integrin-alpha 7, and glycosyltransferases.[61]

X-Linked Inheritance

  • Becker (benign pseudohypertrophic)
  • Duchenne (pseudohypertrophic)

Becker Muscular Dystrophy: Caused by a mutation of muscle protein dystrophin gene, which codes for the protein dystrophin, with 79 exons, by far the largest gene known in humans.[32] This gene transmitted in an X-linked re­cessive manner.[32] Its location is on the small arm (p) of the X chromosome at the Xp21 locus position.[62] Without dystrophin, muscle cells deteriorate or die. The age of onset is 10 to 20 years old, with the distribution of involved muscles to be generalized.[1] 

Duchenne Muscular Dystrophy: Caused by a mutation of the dystrophin gene, located on the small arm (p) of the X chromosome at the Xp21 position.[32] A spontaneous mutation occurs in a third of cases.[63][64] X-linked recessive maternal-fetal transmission occurs in the other two-thirds of cases.[63] The effect is resulting in a non-functional dystrophin protein, which causes similar effects as to that seen in Becker muscular dystrophy. Age of onset is approximately 3 to 5 years of age, with the distribution of involved muscles to be generalized.[61] 

Female Duchenne muscular dystrophy results from an error in female somatic cells whereby one X-chromosome becomes inactivated at an early stage, creating a mosaic representation of heterozygous X-linked genes. This condition generally is sufficient to protect female heterozygotes from X-linked disorders that affect males. However, X-inactivation in the female carrier of an X-autosome translocation can sometimes create a lethal genetic imbalance in half of the body's cells, causing those cells to die. The result is that the same X-chromosome expresses in every cell, and if that chromosome carries a disease allele, the individual can express the X-linked disease like a male, which explains some female cases of Duchenne muscular dystrophy.[65]

* A subtype or classification that is beyond the scope of the article but included for the sake of completeness. 

Epidemiology

  • Most Common Childhood Muscular Dystrophy: Duchenne.[38]
  • Most Common Adult Muscular Dystrophy: Myotonic.[9] 
  • Prevalence Of Muscular Dystrophy (General Population): 16 to 25.1 per 100,000.[66] [67] 
  • Frequency Of Muscular Dystrophy (General Population): 1 per 3,000 to 8,000.[68][69] 
  • Incidence Of Muscular Dystrophy (Male Births): 1 per 5,000 or 200 per 1,000,000.[70]

Becker Muscular Dystrophy 

  • Prevalence (General Population): 4.78 per 100,000.[71]
  • Frequency (Live Male Births): 1 per 18,000.[72] 
  • Incidence (Live Male Births): 1 per 5618.[72]

Congenital Muscular Dystrophy 

  • Prevalence (General Population): 0.99 per 100,000.[71] 
  • Prevalence (Children): 0.82 Per 100,000.[71] 
  • Prevalence (General Population-Italy): 1 per 16,000.[73] 
  • Incidence (General Population-Italy): 0.563 per 100,000.[74]

Duchenne Muscular Dystrophy 

  • Prevalence (General Population): 4.78 per 100,000.[71]  
  • Frequency (General Population): 13 to 33 per 100,000.[75] 
  • Frequency (Males): 1 per 3,500. [20] 
  • Incidence (Live Male Births): 1 per 5,136.[70] 

Emerry-Dreifuss Muscular Dystrophy

  • Prevalence (General Population): 0.39 per 100,000.[71] 
  • Prevalence (Children): 0.22 per 100,000.[71]

Facioscapulohumeral Muscular Dystrophy 

  • Prevalence (General Population): 3.95 per 100,000.[71]
  • Prevalence (Children): 0.29 per 100,000.[71]

Limb-Girdle (Erb) Muscular Dystrophy

  • Prevalence (General Population): 1.63 per 100,000.[71] 
  • Prevalence (Children): 0.48 per 100,000.[71]

Myotonic Muscular Dystrophy 

  • Prevalence (General Population): 8.26 per 100,000.[71] 
  • Prevalence (Children): 1.41 per 100,000.[71]

Oculopharyngeal Muscular Dystrophy 

  • Prevalence (General Population): 0.13 per 100,000.[76]

*US, England, Australia, & Canada unless otherwise specified* 

Pathophysiology

Description

  • Muscle contraction
  • Dystrophin
  • Dystrophin-glycoprotein complex

Muscle Contraction: It is essential first to understand the underlying physiology of muscle cell function. The sliding filament model represents muscle tension as a function that depends on the contraction of the muscle filaments; this is promoted by calcium, which, delivered from the sarcoplasmic reticulum, leads to muscle depolarization. Intracellular calcium binds to the anionic charge of troponin C, which leads to tropomyosin uprooting off of the G-actin site. Once exposed, a myosin head attaches to the presented G-actin site generating a pivot that requires energy in the form of ATP (adenosine triphosphate) to function. This pivot lets filaments made of actin to slide past filaments made of myosin, which achieves muscle shortening, which transfers to the muscle cell's glycoprotein rich cytoskeleton.

Dystrophin: Dystrophin is restricted to the cytoplasmic surface of the muscle fiber plasma membrane and connects the internal cytoskeleton to the extracellular matrix via glycoproteins that traverse the plasma membrane.[32] This cytoskeletal protein renders structural stability to a protein (dystroglycan) complex in cell membranes.[77] More precisely, dystrophin is what anchors the actin cytoskeleton to the basement membrane within a membrane-glycoprotein complex.[77] Dystrophin, laminin, and other proteins are a part of this cytoskeletal framework.[32] Dystrophin connects with F-actin and with β-dystroglycan, which then attaches to α-dystroglycan and laminin within the extracellular matrix (ECM).[32][78] Dystrophin's role is to secure the cytoskeleton to the extracellular matrix.[32] Consequently, if dystrophin is not performing correctly, this modifies tension transmission in a contracting muscle.[1] The contractile actin and myosin proteins normally shorten, which sequentially issues toward both muscle weakness and injury to the cell membrane. Creatine kinase suddenly oozes from every damaged muscle cell and consequently is found in abnormally high levels in the plasma.[79] This CK release additionally incites an inflammatory response that promotes scar tissue formation ending in the classic pseudohypertrophy of the calf muscles linked with muscular dystrophy.[80] Even though the muscles look hypertrophied, there exists a deficiency in working contractile filaments in the tissue and therefore creates weak muscles.[1] The­ deficit is present from fetal development onwards.[81] Phago­cytosis of the damaged muscle cells by inflammatory cells cause scar­ring and further impairment of muscle function.[1]

Dystrophin-Glycoprotein Complex: This protein meshwork seems to strengthen the sarcolemma.[82] The loss of one part of the network may generate changes in other elements. For instance, an initial loss of dystrophin may drive the destruction of sarcoglycans, including dystroglycan.[83] The weakening of the membrane leads to muscle cell death.[1] Skeletal muscle comes to be almost completely substituted with fat and connective tissue.[84] The skeleton even­tually becomes distorted, inducing gradual immobility. Car­diac muscle and smooth muscle of the gastrointestinal tract typically be­come fibrotic.[85] The brain manifests structural deformities with no apparent consistency.[85]

Most Common Findings

  • Chronic respiratory infections precipitated by weakness in the smooth muscle of bronchioles.[23]
  • Impotence caused by gonadal atrophy, which is characteristically associated with myotonic dystrophy.[86] 
  • It is common to possess dysphagia, which is esophageal muscle involvement.[87]
  • Myotonia is a term that describes the inability to relax muscles, which classically manifests as an inability to loosen one's grip or release a handshake.[17] 
  • As a pediatric disease, parents will often complain that their child is clumsy or becomes extremely weak quickly.[88] 
  • Gower sign is when subjects try to stand from a supine position, they "march" their hands and feet to each other).[89] 
  • Weakness and stiffness of distal muscles are usually the presenting symptoms in adolescents with myotonic dystrophy.[15] 

Toxicokinetics

Malignant Hyperthermia: This is a unique and life-threatening myopathy that can occur in genetically susceptive individuals following exposure to triggering factors, usually halogenated anesthetic gases like halothane, isoflurane, sevoflurane, and desflurane.[90] This condition can also manifest from exposure to succinylcholine.[91] These, when given to susceptive individuals, may drive toward extreme skeletal muscle contraction.

Patients with dystrophinopathies produce rhabdomyolysis if exposed to those agents, and many scholars consider it reasonable to utilize non-triggering agents exclusively. Malignant hyperthermia happens because of the irregular calcium control correlated with dytrohpinopathies.

Dysregulated calcium release of the sarcoplasmic reticulum mixed with anesthetic-induced interference of calcium reuptake ends in constant muscle contraction, prolonged aerobic and anaerobic metabolism, driving up carbon dioxide production, elevated end-tidal carbon dioxide, and tachycardia in these individuals who are unable to raise their alveolar minute volume properly. This hypermetabolism generates an exponentially dangerous amount of heat. So much so that the amount of heat appearing overwhelms the body's capacity to dissipate this heat.

History and Physical

Cardiovascular Findings

  • Arrhythmias
  • Congestive heart failure
  • Dilated cardiomyopathy 

Arrhythmias: Cardiac arrhythmias are even more significant in patients with muscular dystrophy. The typical electrocardiogram (ECG) shows increased net RS in lead V1; deep, narrow Q waves from the precordial leads, with tall right precordial R waves in V1.[92] Cardiac disturbances occur commonly in patients with Duchenne muscular dystrophy Type 1 (DM1).[93] Myotonic dystrophy affects the heart muscle, causing arrhythmias and heart block.[94] ECG abnormalities include first-degree heart block and more extensive conduction system involvement. A complete heart block and sudden death can occur.[95]

Congestive Heart Failure: Congestive heart failure seldom occurs except with severe stress, such as pneumonia.[96] Congestive heart failure occurs infrequently but may result from cor pulmonale secondary to respiratory failure.[97] Mitral valve prolapse also occurs commonly.[97]

Dilated Cardiomyopathy: Genetic dilated cardiomyopathies account for 30 to 40% of cases of nonischemic dilated cardiomyopathies.[98] Some are associated with muscular dystrophy. In the skeletal myopathies, a dominant R wave in lead V1 (indicative of prominent posterior wall involvement, by the same mechanism as in posterior wall myocardial infarction).[99] A cardiac cause of death is not always certain despite the presence of cardiomyopathy in almost all patients.[100] The incidence of cardiac involvement in Duchenne muscular dystrophy is as high as 95%.[101] Chronic heart failure may occur in 50% of children.[102]

Musculoskeletal Findings

  • Contractures
  • Delayed motor milestones
  • Expressionless Facies
  • Fractures
  • Gait instability 
  • Gower's sign
  • Muscle wasting
  • Myotonia
  • Pseudohypertrophy
  • Proximal muscle weakness
  • Scoliosis
  • Toe walking

Contractures: Most patients have joint contractures of varying degrees at elbows, hips, knees, and ankles. Contractures that present at birth are referred to as arthrogryposis. Contractures of both the heel cords and iliotibial bands manifest by age six years when toe walking is associated with a lordotic posture. joint contractures and limitations of hip flexion and extension of the knee, elbow, and wrist are made worse by prolonged sitting.[103] Contractures become fixed, and progressive scoliosis often develops that may be associated with pain.[103] Contractures and muscle wasting contribute to muscular atrophy and deformity of the skeleton. Duchenne muscular dystrophy has serious complications.[24] Muscle weakness also leads to contractures of the knees, hips, and other joints, and scoliosis develops in most boys with Duchenne disease.[104] The contractures and skeletal deformities that develop from facioscapulohumeral muscular dystrophy are less often and are less prominent than in Duchenne muscular dystrophy.[105] Other clinical findings include brought about by a futile attempt to overcome foot drop and depressed or absent muscle stretch reflexes.[106]

Delayed Motor Milestones: Duchenne muscular dystrophy is usually identified in children at approximately three years of age when the parents first notice slow motor development.[107] Clinical symptoms often begin between 5 and 15 years of age.[107] Sitting, standing, and walking are developmentally delayed, and the child is clumsy, falls frequently, and has difficulty climbing stairs.[107] Children with Becker muscular dystrophy remain ambulatory into their teens and early 20s; in one study, the average age at the time of necessity for a wheelchair was 25 years.[17] By definition, patients with Becker dystrophy can walk beyond age 15, whereas patients with Duchenne dystrophy typically are wheelchair-bound by age 12.[107]

Expressionless Facies: The inability to close the eyes completely may be noted from early childhood. The face is expressionless, and the pouting of the lips makes whistling impossible. The muscular weakness and wasting produce a" drooping expression." In myotonic dystrophy, the face is hatchet-shaped due to the facial wasting and weakness, and there is bilateral partial ptosis. With bilateral facial palsy, although very rare, it is important to rule out all other possible diagnoses for facial weakness, including upper motor neuron and lower motor neuron disorders, with thorough diagnostic tests.[108]

Fractures: Muscle weakness and inactivity, particularly once a person is in a wheelchair full time, lead to osteoporosis and pathologic fractures. If a fracture occurs, bisphosphonates may help to strengthen bone, although there are no long-term studies on safety in this population.[109]

Gait Instability: The boys stumble repeatedly and have trouble keeping up with friends when playing. Running, jumping, and hopping is always abnormal.[110]

Gower's Sign: This clinical sign can be evoked by asking the child to stand from a sitting position.[111]  Children with muscular dystrophy and other disorders with muscle wasting will not possess the muscle force to stand.[111] They may alternatively first move into a prone position, thrust themselves onto all fours, and suddenly "walk" their hands along their thighs to a standing posture.[111] The appearance of a Gower sign signifies significant proximal muscle weakness. More specifically, it is caused by the weakness of the lumbar and gluteal muscles.[111]

Muscle Wasting: Muscular weakness always begins in the pelvic girdle, causing a "waddling" gait. [107] Hypertrophy of the calf muscles is apparent in 80% of cases.[112] The pattern of muscle wasting present in Becker muscular dystrophy bears a close resemblance to that seen in Duchenne disease. Proximal muscles, particularly of the lower extremities, are prominently involved. As the disease progresses, weakness becomes more generalized.[113] Duchenne weakness worsens over the subsequent few years, resulting in the loss of ability to ambulate by 8 to 13 years of age. Myotonic dystrophy patients have a common "hatchet-faced" look due to temporalis, masseter, and facial muscle atrophy.

Myotonia: TThe word myotonia applies to a prolonged unconscious muscle contraction demonstrated through not being able to loosen grasp. The patient may have a delay in releasing grip when shaking hands. A pause in opening and closing the fists is observable. Myotonia emerges typically at the age of 5 years and is demonstrable through percussion of the thenar eminence, jaw, and musculature of the forearm. Upon forced voluntary closures, myotonia triggers a sluggish relaxation. As muscle deterioration progresses, so does the difficulty of detecting myotonia. It is difficult for people with myotonic dystrophy to relax their grip, in particular whenever the subject is cold.[109][114] 

Pseudohypertrophy: Pseudohypertrophy of the muscle extends to the toes.[115]  Boys will exhibit, in preschool, with muscle weakness, trouble walking, and wide calves (pseudohypertrophy) caused by healthy muscle fiber replacement with fat and connective tissue.[116]  Although the calves are big, the muscle is small. Enlargement of muscles, particularly in the calves, is an early and prominent finding. Congenital can also have calf hypertrophy.[117]

Proximal Muscle Weakness: Proximal muscle weakness may be remarkably apparent when contrasted to distal weakness in many of the conditions listed.[118] Specific evaluation for this, such as arising from a low seat or a squatting posture, is needed.[24] In 3 to 5 years, muscles of the shoulder girdle become affected in Duchenne. This deterioration is succeeded with bilateral sternocleidomastoid and trapezius; myalgias without weakness; winging of the scapula; continuous muscle fiber loss leading to weakness principally of the voluntary muscles; proximal arms and legs. Congenital dystrophy forms may present with hypotonia plus proximal or generalized muscle weakness. Loss of muscle strength is progressive, with leg involvement more severe than arm involvement. 

Between 8 and 10 years of age, walking may require the use of braces. Clinical instability originates in the pelvic girdle, first generating difficulty standing from the floor (Gower sign), climbing stairs, and a waddling gait as a result of the weakness in the lumbar and gluteal muscles.[17] Facioscapulohumeral muscular dystrophy, as the name implies, begins with weakness and atrophy of facial and shoulder girdle (scapulohumeral) muscles.[119] The diagnosis of limb-girdle muscular dystrophy is accepted with the elimination of acute events causing proximal weakness, and the clinical picture, including genetic pattern, excludes Duchenne and facioscapulohumeral muscular dystrophy.[119] Neck muscles, including flexors, sternocleidomastoids, and distal limb muscles, are compromised early in myotonic dystrophy.[17] The weakness of wrist extensors, finger extensors, and intrinsic hand muscles impairs function in myotonic dystrophy.[17] Ankle dorsiflexor weakness may induce a foot drop in myotonic dystrophy.[17] 

Interestingly, contrary to the mechanism of weakness, proximal muscles continue to become more powerful throughout the course in myotonic dystrophy. There is, however, preferential atrophy and weakness of quadriceps muscles in myotonic dystrophy.[17] Scapuloperoneal muscular dystrophy is considered a variant of facioscapulohumeral muscular dystrophy. Their distinction is that the distal muscles in the lower extremity are involved early instead of the facial and shoulder muscle weakness, which is the early sign in facioscapulohumeral dystrophy.[17]

Scoliosis: Once scoliosis begins, it is relentlessly progressive. Curves of more than 20 degrees require surgical intervention to maintain pulmonary function.[120]

Toe Walking: The foot assumes an equinovarus position, and the child tends to walk on the toes because of the weakness of the anterior tibial and peroneal muscles.[121] Patients with muscular dystrophy often toe-walk because of the weakness of the anterior tibial and peroneal muscles, causing the feet to assume a talipes equinovarus position.[122] 

Neurological Findings

  • Cognitive dysfunction
  • Hypersomnia
  • Seizures
  • Visual disturbances

Cognitive Dysfunction: Mild to moderate cognitive problems are common but not universal.[123] Intellectual impairment in Duchenne dystrophy is common; the average intelligence quotient is approximately one standard deviation below the mean.[124] A moderate degree of intellectual disability causes these children to have a mean IQ of approximately 80.[125] Impairment of intellectual function appears to be nonprogressive and affects verbal ability more than performance.[126] Mental retardation may occur in Becker dystrophy, but it is not as common as in Duchenne. The central nervous system is affected in some forms of congenital muscular dystrophy.[127][123]

Hypersomnia: The excessive urge to sleep and daytime somnolence is common.[128]

Seizures: In merosin and FKRP deficiency, only a small number of patients have mental retardation and seizures.[129]

Visual Disturbances: Ocular abnormalities due to eye muscle dysfunction lead to impaired vision.[130] Myotonic dystrophy may present as difficulty in opening eyes after tight closure.[131]

Other Findings

  • Bladder instability
  • Cataracts
  • Frontal baldness
  • Generalized digestive complaints
  • Gonadal atrophy and hypogonadism
  • Insulin resistance

Bladder Instability: Bladder functions are often mildly affected with urinary urgency as a frequent symptom.[132] 

Cataracts: The affected individual may be referred from an ophthalmologist after a recent examination, which revealed the potential for an underlying disorder such as myotonic dystrophy (iridescent spots).[133][134]

Frontal Baldness: This is characteristic of myotonic dystrophy, possibly due to gonadal atrophy and subsequent hypogonadism.[9]

Generalized Digestive Complaints: Smooth muscle dysfunction may cause megacolon, volvulus, cramping pain, and malabsorption in the gastrointestinal tract.[135] Disturbed gastrointestinal peristalsis. Decreased esophageal and colonic motility.[136] Bowel functions are often mildly affected with constipation as a frequent symptom.[137] Some causes of death include aspiration of food and acute gastric dilation. Palatal, pharyngeal, and tongue involvement produce a dysarthric speech, nasal voice, and swallowing problems.[138][139]

Gonadal Atrophy and Hypogonadism: Small soft testes suggesting atrophy are associated with myotonic dystrophy leading to hypogonadism.[140][9]

Insulin Resistance: Diabetes is commonly associated with muscular dystrophy.[141] 

Respiratory Findings

  • Chest deformity
  • Recurrent pulmonary infections
  • Respiratory insufficiency
  • Sleep apnea

Chest Deformity: The chest deformity with scoliosis impairs pulmonary function, which is already diminished by muscle weakness.[142] Examine for gynecomastia, which can be present in patients with myotonic dystrophy. 

Recurrent Pulmonary Infections: By age 16 to 18 years, patients are predisposed to serious, sometimes fatal pulmonary infections.[143] Susceptibility to respiratory tract infections and progressive deterioration of pulmonary function generally lead to premature death, usually into the twenties.[144]

Respiratory Insufficiency: Respiratory failure is the commonest cause of death.[23] Inspection will identify the areas of muscle wasting. A patient presenting with rapid-onset muscle weakness requires an urgent full assessment, as respiratory muscle involvement may lead to respiratory failure.[145] Some patients have a diaphragm and intercostal muscle weakness, resulting in respiratory insufficiency.[10] Progressive course resulting in respiratory complications. Some cases lead to respiratory failure. Pulmonary function is significantly compromised because of marked kyphoscoliosis ("humped" upper spine combined with scoliosis), which usually develops once the child is confined to a wheelchair. As children age, muscle weakness progresses, and respiratory weakness leads to breathing difficulty, particularly when sleeping.[146]

Sleep Apnea: An increased need or desire for sleep is common, as is diminished motivation.[147]

Evaluation

Laboratory Tests

  • Alanine aminotransferase (ALT, SGPT)
  • Aldolase (serum)
  • Arterial blood gases (ABG)
  • Aspartate aminotransferase (AST)
  • Creatine kinase (CK, CPK) and creatine kinase isoenzymes (CK-MB & CK-MM)
  • Lactate dehydrogenase (LDH)
  • Urinalysis (UA)

Alanine Aminotransferase (ALT, SGPT): The normal range in males is 10 to 40 U/L. The normal range in females is 8 to 35 U/L; it is elevated in muscular dystrophy.[19]

Aldolase (Serum): The normal range is 0 to 6 U/L. It is elevated in muscular dystrophy but decreases in later stages of muscular dystrophy.[148]

Arterial Blood Gases (ABG): Normal ranges: PO2 is 75 to 100 mmHg; PCO2 is 35 to 45 mm Hg; HCO3- is 24 to 28 mEq/L; pH is 7.35 to 7.45. Respiratory acidosis can develop if there are defects in muscles involved in respiration.[149]

Aspartate Aminotransferase (AST): Normal ranges from 0 to 35 U/L. Elevated in muscular dystrophy.[19]

Creatine Kinase (CK, CPK) and Creatine Kinase Isoenzymes (CK-MB and CK-MM): Normal ranges from 0 to 130 U/L. Elevated in muscular dystrophy (hyperCKemia).[150] The serum enzymes, especially creatine phosphokinase (CPK), are increased to more than ten times normal, even in infancy and before the onset of weakness.[151] Diagnosis is suggested (a high creatine kinase [CK] level does not confirm the diagnosis because many other alterations can also increase CK) by measuring the blood creatine kinase level, which can be 100 times the normal level, with diagnostic confirmation by genetic testing for mutations in the dystrophin gene.[152] Serum CK levels are invariably elevated between 20 and 100 times normal in Duchenne muscular dystrophy.[153] The levels are abnormal at birth, but values decline late in the disease because of inactivity and loss of muscle mass.[154] Elevated CPK levels at birth are diagnostic indicators of Duchenne muscular dystrophy.[155] The identification of female carriers of the disease is not achievable with certainty, but serum CPK is elevated in 60% to 80% of carriers.[156] Serum CK can be 2- to 20 times above normal in Emery-Dreifuss muscular dystrophy.[157] Myotonic dystrophy may be associated with a normal CK or only mild elevation.[93]

Lactate Dehydrogenase (LDH): Normal ranges from 50 to 150 U/L. Elevated in muscular dystrophy. LDH 4: 3 to 10%, LDH 5: 2 to 9%.[148]

Urinalysis (UA): Glucose in urine is commonly associated with muscular dystrophy due to the high incidence of diabetes mellitus within this population.[158] Myoglobinuria may also be present.[148]

Radiographic Tests 

  • Magnetic Resonance Imaging (MRI)
  • Computerized Tomography (CT)

Magnetic Resonance Imaging (MRI): Coronal T1 weighted MRI may confirm the nonuniform fatty atrophy.[159] There will be a relatively normal sartorius. Lateral radiographs may show cavus foot deformity and diffuse osteopenia.[160] The sagittal view will show diffuse fat replacement of the gastrocnemius & semimembranosus muscles. These changes contribute to the prominent calves typical of affected children.[116]

Computerized Tomography (CT): Axial CT shows denervation hypertrophy of the tensor fascia lata. The muscle becomes enlarged with an increase in intramuscular fat.[161]

Other Tests

  • Chromosomal analysis
  • Electrocardiogram (ECG)
  • Electromyography (EMG)
  • Genetic testing
  • Immunocytochemistry
  • Muscle biopsy
  • Polysomnogram
  • Slit lamp
  • Western blot analysis 

Chromosomal Analysis: DNA testing for common mutations and chromosomal analysis can now rule out Down syndrome, myotonic dystrophy, and other disorders. In both Becker and Duchenne dystrophies, the DNA deletion size does not predict clinical severity.[162] DNA deletion, however, does not change the translational read frame of the messenger RNA in approximately 95 percent of patients suffering from Becker dystrophy. Such "in-frame" mutations allow for the development of dystrophin, which explains for the existence of dystrophin on Western blot examination.[163]

Electrocardiogram (ECG): Often, patients will have annual echocardiograms to stay ahead of any developing cardiomyopathy. This study will demonstrate atrial and atrioventricular rhythm disturbances. The typical electrocardiogram shows an increased net RS in lead V1; deep, narrow Q waves in the precordial leads.[164] A QRS complex too narrow to be right bundle branch block; and tall right precordial R waves in V1.[165] Dominant R wave in lead V1 is the best clue to the actual diagnosis.[166] Normal PR interval, QRS duration. There are abnormal Q waves in the precordial leads. Prominent Q waves lead II.[167]  QRS axis shows deviation.[168] Significant ECG irregularities and diagnosis of atrial tachyarrhythmia are indicators of sudden death.[169] P wave with a prominent early deflection in lead V1 reflects right atrial enlargement.[167]  The ECG could mimic pulmonary hypertension evidenced most notably in lead V1 with QRS right axis deviation.[167] Another less likely cause is an old true posterior wall myocardial infarction. Therefore look for an associated inferior wall myocardial infarction, which will be absent if associated with the dystrophinopathies.[99] The increasing severity of conduction disease is indicated by increasing PR interval and QRS duration.[170] An implantable cardioverter-defibrillator should be considered in all patients.[95]

Electromyography (EMG): Allows assessment for denervation of muscle, myopathies, and myotonic dystrophy, motor neuron disease. EMG demonstrates features typical of myopathy.[171] Clinical examination, electromyography changes are found in almost any muscle: waxing and waning of potentials termed the dive bomber effect.[172]

Genetic Testing: A definitive diagnosis of muscular dystrophy can be established with mutation analysis on peripheral blood leukocytes.[173] Genetic testing demonstrates deletions or duplications of the dystrophin gene in 65% of patients with Becker dystrophy, which is approximately the same percentage as in Duchenne dystrophy.[174] Deletions are usually detected by multiplex polymerase chain reaction (PCR), other mutations by sequencing.[175] Carrier females may be identified by mutation testing or by linkage to intragenic markers allowing for an intragenic recombination rate of 12%.[176]

Immunocytochemistry: A definitive diagnosis of muscular dystrophy can be established based on dystrophin deficiency in a biopsy of muscle tissue.[177] Also, staining of muscle with dystrophin antibodies can demonstrate the absence or deficiency of dystrophin localizing to the sarcolemmal membrane.[1] DIsease carriers may demonstrate a mosaic pattern, but dystrophin analysis of muscle biopsy specimens for carrier detection is not reliable.[178] Immunohistochemistry reveals the absence of emerin staining of myonuclei in X-linked Emery-Dreifuss due to emerin mutations.[179]

Muscle Biopsy: The muscle biopsy shows muscle fibers of varying sizes as well as small groups of necrotic and regenerating fibers. Connective tissue and fat replace lost muscle fibers.  Muscle biopsy usually shows nonspecific dystrophic features, although cases associated with FHL1 mutations have features of myofibrillar myopathy.[180] Muscle biopsy shows muscle atrophy involving Type 1 fibers selectively in 50 percent of cases.[15] Typically various agentic nuclei can be observed in muscle cells as well as in dysplastic fibers with intracytoplasmic nuclear clusters.[181] Histologic changes in muscle include degeneration of muscle fibers, with variation in fiber size and central nuclei.[182] The individual with Scapuloperoneal muscular dystrophy will have fiber splitting and fibers that appear profusely "moth-eaten" and whorled.[183]

Polysomnogram: Excessive daytime somnolence with or without sleep apnea is not uncommon. Sleep studies, noninvasive respiratory support (biphasic positive airway pressure [BiPAP]), and treatment with modafinil may be beneficial.[184]

Slit Lamp: An examination for cataracts that may be present in patients with muscular dystrophy.[185]

Western Blot: A diagnosis of Duchenne dystrophy can also be made by Western blot analysis of muscle biopsy specimens, revealing abnormalities on the quantity and molecular weight of dystrophin protein. On Western blot, Becker muscular dystrophy individuals dystrophin levels will appear normal, although the protein itself is abnormal; this is in comparison to Duchenne muscular dystrophy affected individuals who have a significantly decreased dystrophin on Western blot.[186]

Treatment / Management

Medical Interventions

  • Anti-arrhythmics
  • Anti-epileptics
  • Anti-myotonic drugs
  • Non-steroidal anti-inflammatory drugs (NSAIDs)
  • Steroids

Anti-Arrhythmics: The pharmacological treatment of patients with a prevalent involvement of the cardiac tissue conduction relies on the use of ACE-inhibitors and appropriate antiarrhythmic drugs. In the case of atrial arrhythmias, the preference is for drugs such as antiarrhythmics (flecainide, propafenone) and beta-blockers. Amiodarone should be limited to patients who do not respond to the previous drugs, taking in mind that these are young patients, long-term therapy, and a high risk of adverse effects on the thyroid and pulmonary function.[187]

Anti-Epileptics: Children need to be followed closely by neurologists. Management of epilepsy is necessary for some patients.[188]

Anti-Myotonics: The pain associated with muscle rigidity is greatly alarming in the patient.[189] When myotonia is disabling, treatment with a sodium channel blocker such as phenytoin (100 mg orally three times daily), procainamide (0.5–1 g orally four times daily), or mexiletine (150 to 200 mg orally three times daily) may prove helpful, but the associated side effects, particularly for antiarrhythmic medications, are often limiting.[190] The preferred drug for a symptomatic patient requiring anti-myotonia medication is phenytoin and mexiletine; other medications, especially quinine and procainamide, can cause an increase in the risk of cardiovascular complications.[191]

Non-Steroidal Anti-Inflammatory Drugs: Treatment involves the administration of non-steroidal anti-inflammatory drugs to decrease pain and inflammation.[192]

Steroids: Glucocorticoids, administered as prednisone in a dose of 0.75 mg/kg per day, significantly slow progression of muscular dystrophy for up to 3 years.[193] Some patients cannot tolerate glucocorticoid therapy; weight gain and increased risk of fractures, in particular, represent a significant deterrent.[194] There is recent evidence that oral steroids early in the disease can lead to dramatically improved outcomes.[195] Children can walk an additional 2 to 5 years, and life expectancy has increased.[12] Researchers have not adequately studied the use of glucocorticoids in Becker dystrophy.[196] Some individuals with facioscapulohumeral muscular dystrophy improve with steroid therapy, particularly if the clinical picture includes rapidly progressive weakness.[197] The evidence is not clear on if steroids are useful for the treatment of myotonic muscular dystrophy.[198]

Golodirsen (SRP-4053): This drug is an antisense therapy used for the treatment of Duchenne muscular dystrophy. Patients need to have a confirmed mutation of the dystrophin gene to facilitate exon 53 skipping. It is FDA approved, but the evidence to support its use is not yet well established.[199][200]

Surgical Interventions

  • Defibrillator or a cardiac pacemaker
  • Contracture release
  • Shoulder surgery
  • Spinal correction

Contracture Release: Surgical release of contracture deformities is used to maintain normal function as long as possible.[201] Massage and heat treatments also may be helpful.

Defibrillator or Cardiac Pacemaker: Cardiac function requires monitoring, and pacemaker placement may be a consideration if there is evidence of heart block.[95] Management of cardiomyopathy and arrhythmias may be life-saving.[95] In patients with severe syncope, established conduction system disorders with second-degree heart block previously documented, or tri-fascicular conduction abnormalities with significant PR interval lengthening, consideration needs to be given towards placement of a cardiac pacemaker.[202] An advanced cardiac block is also an indication to install a pacemaker.[203]

Shoulder Surgery: Individuals with facioscapulohumeral muscular dystrophy may benefit from surgery to stabilize the shoulder.[204]

Spinal Correction: Scoliotic surgery is an option when curves exceed 20 degrees to prolong respiratory function or walking ability or both.[120]

Other Interventions

  • Supportive physiotherapy 
  • Supportive bracing
  • Supportive counseling
  • Genetic counseling

In addition to pharmacologic intervention, general supportive care may be beneficial, including physical therapy, range of motion exercises, padding, skincare, orthotics, and safety awareness.

Supportive Physiotherapy: Treatment includes supportive physiotherapy to prevent contractures and prolong ambulation.[64] Maintaining function in unaffected muscle groups for as long as possible is the primary goal. Although activity fosters maintenance of muscle function, strenuous exercise may hasten the breakdown of muscle fibers.[205]

Supportive Bracing: This helps to maintain normal function as long as possible  Proper wheelchair seating is essential. Molded ankle-foot orthoses help stabilize gait in patients with foot drop.[206] Lightweight plastic ankle-foot orthoses (AFOs) for footdrop are extremely helpful. Footdrop is easily treatable with AFOs.[207] Individuals with scapuloperoneal muscular dystrophy remain ambulatory for 40 or more years.[208]  Occasionally, walking may become hampered by paraspinal muscle contractures; in that case, a wheelchair may assist the individual when it is necessary to cover long distances.[103] Bracing may be performed for function; for example, dorsiflexion of the feet with ankle-foot orthotics to prevent tripping or to provide support and comfort.[103]

Supportive Counseling: Some forms of muscular dystrophy may be arrested for prolonged periods, and most patients remain active with a normal life expectancy.[209] Thus, vocational training and supportive counseling are important to provide the information necessary to plan their future.

Genetic Counseling — Genetic counseling is recommended.[210] With X-linked inheritance, male siblings of an affected child have a 50% chance of being affected, and female siblings have a 50% chance of being carriers. If the affected individual marries and has children, all daughters will be carriers of this X-linked recessive disorder. Genetic counseling should be offered to the mother, female siblings, offspring, and any maternal relatives.

Differential Diagnosis

Differential Diagnosis For Associated Signs And Symptoms

Utilizing the following mnemonics will aid in the recall of the differential diagnoses associated with the weakness and ataxia of muscular dystrophy:

Ataxia (Can't Stand Very Well)

  • Cerebellar Ataxia
  • Sensory Ataxia
  • Vestibular Ataxia
  • Weakness

Ataxia, Acute (U.N.A.B.L.E. T.O. S.T.A.N.D.)

  • Underlying weakness (may mimic ataxia)
  • Nutritional neuropathy (vitamin B12 deficiency)
  • Arteritis/vasculitis
  • Basilar migraine
  • Labyrinthitis/vestibular neuronitis
  • Encephalitis/infection
  • Trauma (postconcussive)
  • Other (rare metabolic or genetic diseases)
  • Stroke (ischemia or hemorrhage)
  • Toxins (drugs, toluene, mercury)
  • Alcohol Intoxication
  • Neoplasm/paraneoplastic syndromes
  • Demyelination (Miller Fisher, Guillain Barre, MS)

Ataxia, Chronic (C.A.N.T. S.T.A.N.D.)

  • Congenital malformation/Chiari
  • Autosomal recessive ataxias
  • Nutritional (vitamin B12 deficiency)
  • Trauma (postconcussive)
  • Stroke (ischemia or hemorrhage)
  • Toxins (drugs, toluene, mercury)
  • Alcohol Intoxication/Autosomal dominant ataxia
  • Neoplasm/paraneoplastic syndromes
  • Demyelination (MS)

Weakness, Acute (M.I.S.S. G.I.M.P)

  • Myelopathy (acute) / myopathy
  • Infection
  • Stroke
  • Systemic illness
  • Guillain-Barre syndrome
  • Iatrogenic/drugs
  • Myasthenia
  • Paralytic toxins/periodic paralysis

Weakness, Chronic (G, I.' A.M. L.I.M.P, C.A.N.T. S.T.A.N.D.)

  • Guillain-Barré syndrome
  • Iatrogenic (paralytic agents, aminoglycosides, steroids)
  • Myopathy/myositis
  • Lou Gehrig disease (ALS, motor neuron disease-usually gradual)
  • Infection (polio, botulism)
  • Myelopathy (acute).
  • Periodic paralysis, porphyria, paraproteinemia
  • Cushing's
  • Arteritis/vasculitis/stroke
  • Neoplastic (meningitis, paraneoplastic)
  • Toxins (lead, arsenic, pufferfish, tick paralysis)
  • * Acute/subacute, bilateral with minimal sensory involvement
  • Systemic illness (anemia)
  • Thyroid
  • Addison's
  • Neuromuscular junction disease (Myasthenia, Lambert-Eaton syndrome)
  • Diabetic amyotrophy 

Diseases Or Conditions Potentially Mistaken For This Disease

  • Acid maltase deficiency
  • Drug-induced myopathy
  • Dermatomyositis sine dermatitis
  • Endocrinopathy
  • "Fatigue" syndromes
  • Inclusion body myositis
  • Late-onset spinal muscular atrophy
  • McArdle's deficiency (myophosphorylase deficiency)
  • Metabolic myopathies
  • Motor neuron disease
  • Neurogenic disorders
  • Polymyositis

Diseases Or Conditions That Must Be Ruled Out

While muscular dystrophy is not a diagnosis of exclusion, it is often confused for several diseases due to their overlapping etiologies. The clinician must exclude the following diseases in a patient with a muscular disorder, which can otherwise cause significant morbidity and mortality:

  • Adrenal insufficiency
  • Electrolyte imbalance: sodium, potassium, and magnesium
  • Hypercalcemia
  • Porphyrias
  • Rabies
  • Complicated migraine
  • Postictal (Todd's) paralysis
  • Hypoglycemia

Acute spastic paraparesis is a medical emergency. The clinician should strongly suspect myasthenia gravis in any patient who reports excessive weakness at the end of the day. Consider Pancoast tumor of the lung in a patient presenting with upper limb weakness and painful neuropathy secondary to neoplastic infiltration of the lower trunk of the brachial plexus, particularly when Horner syndrome is present. Paraneoplastic syndromes must also merit consideration in the diagnosis. Rule out lesions of extrapyramidal tracts or cerebellar pathways which may also present as weakness, but without objective evidence of decreased muscle strength.

An acute onset gait disorder is likely to be due to acute systemic decompensation; a careful, systematic evaluation can exclude such catastrophic presentations. It is not advisable to attribute gait disorder to one single disease. An abnormal gait may be a risk factor for falls. Difficulty with getting out of a chair without arm support and initiate movement suggests limb-girdle dystrophy. 

Gait abnormalities can indicate a serious medical emergency, especially when the problem is associated with any of these additional symptoms:

  • Headache (raised intracranial pressure)
  • Nausea or vomiting
  • Decreased alertness
  • Impaired coordination presenting on only one side of the body
  • Recent viral illness/immunization (Guillain-Barré syndrome)
  • Trauma.

Discussion 

Muscular dystrophy may be mistaken for polymyositis, most often when the duration of symptoms appears to be short. The pattern of weakness may be very helpful in making a distinction. Secondary inflammatory infiltrates may cause pathological confusion, especially in limb-girdle muscular dystrophy and facioscapulohumeral muscular dystrophy.

Are Reflexes Hypoactive? The presence of hypoactive reflexes would suggest myotonic dystrophy, tabes dorsalis, and progressive muscular atrophy.[17] This presentation can also just be weakness causing diminished reflexes.

Is There Any Pain Present? The typical features of muscle disease are weakness, potentially relative to exercise, and, on occasions, muscle pain (myalgia). Conversely, a short history of painful weakness in adulthood, would suggest an inflammatory myositis.[211]

Is The Problem Acute Or Chronic? The age and rate of progression are often helpful in determining the type of muscle disease. Progressive slow weakness absent pain from childhood would suggest degenerative muscular dystrophy. Dreifuss muscular dystrophy and Bethlem myopathy cause fixed contractors that occur early and represent distinctive features of these diseases.[24]

Is Weakness Primarily Distal Or Proximal? The distribution of weakness is also of assistance in defining the likely type of muscle disease, proximal arm, and leg weakness present in limb-girdle muscular dystrophy.[17]

Is The Weakness Localized Or Diffuse? Muscle weakness may be from a myopathy such as dermatomyositis, an inflammatory disease such as rheumatoid arthritis, a neurologic disorder such as Guillain-Barré syndrome, or an infection such as Lyme disease or trichinosis.[17]

Are There Any Focal Neurological Lesions? Myotonic dystrophy, myasthenia gravis, and progressive muscular atrophy may present with partial ptosis.[17]

Prognosis

Morbidity

People with dystrophies having significant heart involvement may nonetheless have almost average life spans, provided that cardiac complications are monitored and aggressively treated.[99] Maintaining ambulation and careful follow-up for evidence of cardiopulmonary complications are essential for long-term care. Although there have been significant advances in the treatment of muscular dystrophy, the disease is still incurable and cannot be prevented. Most patients die before the age of 30 years due to cardiopulmonary failure.[212] Patients can have a better quality of life with proper care.

Mortality 

Duchenne muscular dystrophy can survive around 20 years, but the condition is fatal in 100% of cases.[212] Walker-Warburg syndrome is the most severe of the congenital muscular dystrophies, causing death by one year of age.[213] Patients with Becker dystrophy have a reduced life expectancy, but most survive into the fourth or fifth decade.[213] Children with Duchenne muscular dystrophy usually succumb to other pulmonary or cardiac causes, and death ensues by the late teens. Only 25% live to age 21.[213] Severe cardiac and respiratory problems develop in the late teen years and into the early 20s. Other causes of death include aspiration of food and acute gastric dilation.[213] Life expectancy is normal in patients with facioscapulohumeral dystrophy.[213] 

Complications

Considerations

  • Anesthesia risk
  • Bone demineralization
  • Cardiopulmonary disease
  • Disability

Anesthesia Risk: Patients with muscular dystrophy tend to do poorly after the administration of general anesthetic and will require intensive postoperative observation.[214]

Bone Demineralization: Osteopenia and osteoporosis due to decreased mobilization and immobilization; this can give rise to fractures and scoliosis.[214]

Cardiopulmonary Disease: Frequent follow-up to eliminate secondary complications such as cardiopulmonary disease or cardiac failure due to cardiomyopathy.[214]

Disability: Disability and dependence on walking aids like wheelchairs due to muscular injuries and contractures.[214]

Enhancing Healthcare Team Outcomes

Skills

Adolescents with muscular dystrophy need an interprofessional plan of care, including consideration to heart and breathing difficulties, weight loss/gain, constipation, rehabilitative/developmental difficulties, psychosocial requirements, and neurologic and orthopedic problems.[214] [Level 2]

Strategy

A regulated method for gathering and communicating data helps to support overall performance across programs, sites, and organizations.[64] [Level 2] Therefore, it further enhances the quality of care and decreases disparities in health care delivery through standardization of care. Clinicians and their institutions are enthusiastic in advancing early diagnosis of muscular dystrophy; thus, the strategic indicator for evaluation might be the proportion of patients who receive genetic testing or are offered genetic testing. Clarifying care goals from the beginning allows other team members a framework from which to define their indicators of success more clearly.[64] [Level 2]

Ethics and Responsibilities

Primary care providers may serve as the arbiter of treatment for the various aspects of the disease as well as other problems. Therefore, all other team members now have one centralized point of contact to align with when making decisions on supportive and assistive measures. This point is important because proper implementation and monitoring is a crucial component of management.[64] [Level 2]

Interprofessional Communication 

Another crucial aspect to the management of patients with muscular dystrophy, especially for those with chronic, progressive, and severe forms, relates to patients' need to be informed about research efforts for "their" disease. Because of Internet access and lay support groups, patients today are more familiarized with their disease than ever before. They want to know about current research and relevant ongoing clinical trials, the role of alternative therapies, and other issues and questions.  

All members of the healthcare team must therefore always be ready to provide solid information about a patient's condition by keeping up with fellow team members about what each member's profession can offer in terms of information. This approach facilitates communication that centers around the patient and less around the disease of a given patient and may involve something as simple as providing patients with information on support groups or informative websites. Patients should be encouraged to participate as much as deemed feasible and practical. It is crucial to help patients and their families shift out of a passive mindset and realize that they have a role in their treatment too.[214] [Level 2]

Care Coordination

Effective management will require an interprofessional approach that includes a diverse team of health care professionals.: Strength team members are those aimed at improving strength (e.g., prednisone, stretching). Supportive team members are those who focus on the problems resulting directly from muscle weakness such as respiratory distress. Symptomatic team members are those whose aim is to treat issues that are not directly related to muscle disease but are part of the condition. Examples include cardiac arrhythmias in myotonic dystrophy; and psychological team members whose goal is to improve the patient's mental outlook and provide up to date information about their diseases. An interprofessional team member approach offers a useful conceptual framework and allows for proper delegation of responsibilities.[214] [Level 2]


Article Details

Article Author

Andrew LaPelusa

Article Editor:

Michael Kentris

Updated:

7/21/2021 11:43:56 PM

PubMed Link:

Muscular Dystrophy

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