Introduction

In 1841, a British anatomist, Alfred Poland, discovered a rare congenital chest wall muscle deficiency that he later named Poland syndrome (PS). Poland syndrome most frequently involves unilateral underdevelopment or absence of chest wall muscle that is present at birth with some associated anomalies of the hand/upper extremity on the same side. Rarely, it is found to have bilateral chest muscle deficiency involvement. Some even suggest an association with vascular, skeletal, and inner organ anomalies. There is extensive variation in the presentation of Poland syndrome, which can sometimes make it difficult to diagnose.[1][2]

Etiology

Controversy exists over the etiology of Poland syndrome. It mostly occurs sporadically. However, three other theories about the development of Poland syndrome include genetic, teratogenic, or vascular compromise during fetal development as possible etiologies. There has been documentation that distant family members developed Poland syndrome supporting the theory that it may be genetically linked. Another theory is that Poland syndrome results from environmental or medication-induced teratogenic effects on a developing fetus. Researchers found a higher incidence in pregnant smokers compared to pregnant non-smokers during embryogenesis.[3] 

Other studies indicate medication-induced abortions for unwanted pregnancies with failed interruption of pregnancy as an induction factor of Poland syndrome. Some suggest vascular compromise during fetal development. These usually present with hypoplasia of subclavian or axillary vessels in Poland syndrome, which support the theory of a poor developing limb bud. This could be caused by many factors such as amniotic bands, tumors, edema, or aberrant muscle during the sixth and seventh weeks of embryogenesis.[2]

Epidemiology

The incidence of Poland syndrome ranges between one in 10,000 to 100,000 in live births.[3] In general, males are affected three times more than females. Right-sided anomalies are usually twice as predominant as left-sided. Most Poland syndrome is found sporadically with some occasional familial genetic descendants. Additionally, mild forms are also more common than severe forms, suggesting that many cases are missed or under-represented. These aspects can underestimate the incidence rate overall.[1]

Pathophysiology

Poland syndrome has a wide diversity of clinical presentations. The congenital deformity can extend to anomalies of the pectoral muscle, breast, nipple complex, axillary fold, soft tissue, ribs, and upper limb.[4] The classic pattern is unilateral hypoplasia or aplasia of the sternocostal head of pectoralis major muscle and an ipsilateral hypoplastic hand with simple syndactyly and short webbed fingers. In females, it is sometimes accompanied by underdeveloped breast tissue on the pectoral muscle deficiency side.[5] When the absence of the breast in females is found to be the leading feature of the Poland syndrome, it is also known as “Amazone syndrome,” which was described by Mühlbauer in 1977. It was suggested that the extremity bud damage and the proximity of the lacteal mound during embryogenesis results in the lack of development of breast tissue described in Amazone syndrome.[2][6]

Poland syndrome has also been occasionally associated with vascular, skeletal, and inner organ anomalies, including subclavian and axillary vascular system variances, scoliosis, sternal and rib abnormalities, and even dextrocardia.[7]

Symbrachydactyly, sometimes referred to as “atypical cleft hand,” is a congenital limb abnormality describing hand malformations involving brachydactyly (short fingers), syndactyly (union of 2 or more fingers), and global hypoplasia of the hand. These can include transverse deficiency (congenital amputation), central deficiency (absence of one or more digits in which the central rays of hand affected), brachymetacarpia (shortened metacarpal bone and finger), brachyphalangism (shortened phalanges), and hypodactyly (fewer than the normal number of fingers). All these anomalies describe different forms and severity of hand conditions that can present in patients with Poland syndrome.[8]

History and Physical

Typical Poland syndrome presentations are aesthetical complaints regarding chest asymmetry. Most patients are found to be asymptomatic.[9] Children usually present first with finger or hand anomalies as the chest wall asymmetry appears to be more obvious as they age. In rare instances, the severe PS cases can present with obvious scoliosis, rib, and sternum deformity, which causes cardiopulmonary symptoms such as shortness of breath or difficulty taking deep breaths. 

The examination begins by assessing the anterior chest wall for asymmetry. The presentation of chest wall tissue deficiency is highly variable. The pathognomonic finding is the absence of the sternocostal head of the pectoralis major muscle. Other structures, which may be absent, include ribs 2 to 5, latissimus dorsi, serratus anterior, and pectoralis minor. The presence or absence of the latissimus dorsi muscle is of great importance in terms of surgical planning. The sternum and ribs may appear distorted or hypoplastic. The ipsilateral breast and/or nipple-areola complex may be absent or hypoplastic. The ipsilateral hand may have defects such as syndactyly, microdactyly, brachysyndactyly, or hypoplasia of the hand.

The patient may also present with a variation of scoliosis and anterior chest wall defects such as pectus excavatum.[5] Visual inspection and palpation of the chest wall are important aspects of the physical evaluation that determine the muscle deficiencies and the bony deformities. Soft tissue on the affected side is usually thinner with sometimes associated alopecia on the involved side.[10] The axilla and back should also be carefully examined to observe. Auscultation of the cardiopulmonary system is also a primordial part of the examination to rule out dextrocardia, a rare form of Poland syndrome that can be seen when the left side is involved.[11]

Evaluation

The only defining criterion in the diversity and variation of Poland syndrome is the pectoral muscle deficiency.[12]

Differential Diagnosis

• Simple breast asymmetry
• Amazone syndrome
• Congenital thoracic anomalies
• Congenital upper limb anomalies 
• Congenital breast anomalies
• Swyer-James syndrome[12][22][23][24]

Staging

Most physicians use a classification system for Poland syndrome using grade I-III to qualify the different degrees of severity. The grading system is also referred to as Foucras’s classification.[19]

• Grade I is usually a mild chest deformity with pectoralis major hypoplasia, moderate breast hypoplasia. It illustrates on examination as slight chest wall asymmetry in men and breast asymmetry in women.
• Grade II involves marked pectoralis major aplasia, hypoplasia, or other chest wall muscles, with possible rib deformity. It demonstrates a marked chest wall asymmetry in men and marked breast asymmetry in women.
• Grade III comprises full muscular and breast aplasia, including aplasia of other chest wall muscles with major bone and cartilage anomaly, including rib and sternal deformity. On physical exam, it will present as major chest wall asymmetry in men and women and breast asymmetry with aplasia in women.

Prognosis

In a few research studies, some malignancies have been found to be associated with Poland syndrome, such as leukemia and carcinoma of the hypoplastic breast and other tumors. The relationship between congenital defect and tumors push to oncologic awareness.[16] The majority of children with Poland syndrome will reach adulthood, and in general, it is considered to have a decent prognosis.

Complications

Complications of Poland syndrome patients are not commonly heard of as most patients are asymptomatic. The young children who present with few musculoskeletal dysfunctions are corrected at such an early age that they are usually not considered a true complication.[25]

Surgical treatment options for Poland syndrome come with their own expected surgical complications. Autologous fat transfer can sometimes postoperatively get complicated with fat necrosis that can get corrected after surgical drainage. Another long-term complication from fat grafting is liponecrotic cysts formation, which has benign characteristics on breast imaging.[17] Breast reconstruction complications, in general, include infection, bleeding, and poor healing of scars. Flap surgery complications involve possible risk of loss of flap tissue, either complete or partial, possible loss of sensation at the flap donor and reconstruction site.[26] Chest wall implants can sometimes postoperatively develop a seroma, infection, displacement, rupture, or capsule formation.[27]

Deterrence and Patient Education

The low incidence and unusual presentation of this syndrome, presenting at a young age in children, makes it sometimes difficult to diagnose and explain to distressed parents. Therefore, it is a crucial aspect of patient education, and awareness as this chest wall abnormality is usually confused and unrecognized for asymmetry by family members until perceived by their pediatricians during physical exams.

Enhancing Healthcare Team Outcomes

Poland Syndrome is an unfortunate congenital muscle deficiency that affects young children with disfiguring outcomes. It is a mental and physical disturbance that can affect patients over their entire lifespan if not treated accordingly. The goal of these patients is to use integrated care with different evidence base approach and planning to address their aesthetic concerns with plastic reconstruction and their psychological disorder with psychotherapy support. An interprofessional approach that provides a synergistic and integrated team dedicated to patient care can help achieve the best possible outcomes for Poland syndrome patients.[28]

The role of early cosmetic reconstruction and mental health support at a young age cannot be undermined. If the patient is to be discharged home after surgical reconstruction, consultation should be made with a social worker, physical therapist, and community mental health therapist who can monitor the patient's progress to evaluate for proper recovery and make referrals as needed. An integrated collaboration of different medical team sharing decision making, plan of action, and communication are important for a successful long-term outcome.[28][6]