Continuing Education Activity

Ainhum, or dactylolysis spontanea, is a rare medical condition characterized by developing fibrotic constricting bands that usually form around the digits. These fibrous tissue rings can lead to significant morbidity and auto-amputation of the affected digit. Although, historically, ainhum was recognized in South American and African individuals, it is now reported in a more diverse population, including White individuals and, rarely, in India. Importantly, this condition requires differentiation from other hereditary and secondary constricting band diseases. This activity outlines the epidemiology, clinical manifestations, diagnosis, and management of ainhum for the interprofessional healthcare team to treat patients with this condition and improve the overall outcomes.

Objectives:

• Differentiate ainhum from other hereditary and secondary constricting band diseases based on clinical presentation and diagnostic findings.

• Screen patients with relevant risk factors, particularly those from regions with historical prevalence, for early signs and symptoms of ainhum, promoting early detection and intervention.

• Implement evidence-based diagnostic and management strategies for ainhum, including surgical and nonsurgical approaches, in alignment with established clinical guidelines.

• Coordinate long-term follow-up and care plans for patients with ainhum, emphasizing the importance of ongoing monitoring, pain management, and psychological support to enhance overall quality of life.

Introduction

Ainhum, or dactylolysis spontanea, is a rare medical condition characterized by the development of fibrotic constricting rings at the base of one or multiple toes. These fibrous tissue rings can lead to significant morbidity and auto-amputation of the affected digit. Historically, ainhum is more prevalent in males than females, and this condition is recognized in a more diverse population, including South American, African, and White individuals, as well as in India.[1] Initially described by Silva Lima in 1867, the term "ainhum" originates from the Nago word meaning "fissure" or the Yago word meaning "to saw or cut."[1][2][3] 

Etiology

The exact etiology of ainhum is unknown. The prevalence of ainhum in individuals of African descent suggests a genetic predisposition to developing an excessive fibrous tissue response in reaction to mechanical or infectious injuries.[3] Pseudoainhum occurs when an underlying cutaneous condition or irritation leads to the development of a fibrotic band.[1][2][4][5] Pseudoainhum can be attributed to amniotic bands, the entanglement of hair or thread around a digit, and the mechanical effects of hyperkeratosis in individuals with palmoplantar keratoderma.[3]

Epidemiology

Ainhum predominantly affects males of African descent, usually between the ages of 30 and 50. The overall prevalence of ainhum in the population ranges from 0.015% to 2.2%, with a male-to-female ratio of 2:1, indicating a higher incidence in males.[5] Although ainhum has a worldwide prevalence, this condition is most commonly observed in African countries. Most case reports of ainhum in White patients originate from Brazil, which is another endemic region, and this occurrence may be associated with interethnic marriages.[1] 

Pathophysiology

True ainhum is considered as a rare idiopathic condition.[2] Patients affected by ainhum present with the development of a fibrotic band around the base of a toe or, less commonly, a finger. Although this condition primarily affects the fifth toe, in approximately 75% of cases, both feet are involved. Distal to the fibrotic band, the digit experiences swelling caused by lymphedema, and over time, there is bone resorption. Auto-amputation of the digit typically occurs after 4 to 6 years. The frequent association between walking barefoot in tropical regions and constricting bands of the feet in rural areas of Africa and South America has led to speculation about the potential impacts of ainhum.[2]

Histopathology

Although biopsies are usually unnecessary for diagnosis, they may reveal dermal fibrosis with longitudinally oriented connective tissue when performed. Electron micrographic findings often resemble those of keloidal tissue.[6]

History and Physical

Clinically, the primary feature of ainhum is the progressive development of a circumscribed fibrotic ring at the base of the toes or, less commonly, the fingers.[1] The most commonly affected location is typically above the fifth toe, and this condition often appears on both sides (bilateral).[2][7] In ainhum, a fibrotic band typically develops within a flexural groove, and the circumferential lesion gradually advances, causing alterations distal to the constriction.

The clinical criteria comprise the following 3 distinct findings in patients with ainhum:[2]

• Soft tissue constriction
• Bulbous distal enlargement
• Distal thinning or lysis of phalangeal bones

Cole identified and categorized ainhum into the following 4 distinct clinical stages:[2][8]

•  A small callus develops and eventually transforms into a circumferential groove or fissure.

• The portion distant to the band becomes bulbous or globular due to impaired lymph and venous drainage, as well as narrowing of arteries and bone.

• Pain develops as the bone undergoes separation, either intraosseously or intra-articularly, resulting in increased mobility of the affected digit.

• Bloodless and spontaneous auto-amputation of the digit occurs.

Evaluation

Ainhum is predominantly diagnosed through clinical evaluation. During the initial presentation, a fissure beneath the toe may appear nonspecific. The diagnosis of the condition is confirmed after the development of the fibrotic ring. Distinguishing ainhum from pseudoainhum is crucial.

Radiography is valuable for assessing the extent of the condition. The progressive features associated with ainhum can also be identified through plain films, ultrasound, computed tomography, or magnetic resonance imaging. Radiographs will initially show a radiolucent band at the base of the toe, followed by swelling. Eventually, osteolysis becomes apparent distal to the band. The bone continues to constrict until autoamputation occurs. 

Treatment / Management

Currently, no consistent treatment approach or targeted therapies have been established for ainhum, as the inciting event is often unidentified. Some attempts have been made using topical and injectable corticosteroids, retinoids, or salicylates to manage early lesions.[2][9] There are reports of a case in which psoriasis caused pseudoainhum, but it was successfully treated with a combination of topical pimecrolimus and low-dose narrowband UVB therapy.[10] However, extrapolating this to idiopathic ainhum appears unlikely, as this particular patient responded to treatment of the underlying causal condition. Early intervention aimed at addressing the constricting rings of fibrous tissue, akin to treating scars and contractures, may be beneficial.[1][2]

Resection of the fibrous band followed by a Z-plasty surgical technique may help prevent progression if the procedure is conducted in the early stages.[1][11] The anticipated outcomes of the procedure involve either surgical amputation after bone separation or auto-amputation.

Differential Diagnosis

Clinically, the primary feature of ainhum is the progressive development of a circumscribed fibrotic ring at the base of the toes or, less commonly, the fingers.[1] The most commonly affected location is typically above the fifth toe, and this condition often appears on both sides (bilateral).[2][7] In ainhum, a fibrotic band typically develops within a flexural groove, and the circumferential lesion gradually advances, causing alterations distal to the constriction.

The clinical criteria comprise the following 3 distinct findings in patients with ainhum:[2]

• Soft tissue constriction
• Bulbous distal enlargement
• Distal thinning or lysis of phalangeal bones

Cole identified and categorized ainhum into the following 4 distinct clinical stages:[2][8]

• A small callus develops and eventually transforms into a circumferential groove or fissure.

• The portion distant to the band becomes bulbous or globular due to impaired lymph and venous drainage, as well as narrowing of arteries and bone.

• Pain develops as the bone undergoes separation, either intraosseously or intra-articularly, resulting in increased mobility of the affected digit.

• Bloodless and spontaneous auto-amputation of the digit occurs.

Pseudoainhum

Pseudoainhum occurs due to an underlying cutaneous disorder or an identifiable trigger.[1][2][4]

Congenital pseudoainhum

Amniotic band syndrome, also known as Streeter dysplasia, is believed to be a consequence of the rupture of amniotic membranes and subsequent constriction of developing fetal tissue. Variable clinical manifestations include constricting rings, digital amputations, or acrosyndactyly. More severe consequences may include anencephaly, lymphedema, and limb amputations.[12]

Acquired pseudoainhum

Acquired pseudoainhum develops either due to a hair or thread acting as a tourniquet around a digit or in association with palmoplantar keratoderma or, occasionally, other dermatoses. Keratodermas that may present with autoamputation include Vohwinkle syndrome, Olmsted syndrome, Mal de Meleda, loricrin keratoderma, keratosis linearis with ichthyosis congenita and sclerosing keratoderma syndrome (KLICK syndrome), and Papillon-Lefèvre syndrome.[13]

Acquired dermatoses and other conditions that can lead to the appearance of constricting bands include leprosy, tertiary syphilis, scleroderma, Raynaud syndrome, syringomyelia, diabetes, psoriasis, neuropathic plica, systemic sclerosis, yaws, spinal cord tumors, liver cirrhosis, and factitious pseudoainhum (from tourniquet application).[1][14]

Prognosis

Ainhum progresses gradually, and spontaneous amputation typically occurs 4 to 6 years after disease onset.[1]

Complications

Complications of ainhum are secondary infection, pain, imbalance, deformity, and psychological effects stemming from physical mutilation and ongoing pain.[2]

Postoperative and Rehabilitation Care

Although not explicitly documented, some clinicians suggest that patients with ainhum or other constricting band syndromes could benefit from physical and occupational therapies. Occupational therapy may improve mobility and potentially enhance fine motor function following amputation for patients in the early stages of the disease. Patients who have undergone surgical or spontaneous amputation of the digits of the foot may benefit from physical therapy or custom orthotics to address locomotor dysfunction and improve balance.

Consultations

As the diagnosis relies on clinical evaluation, dermatology clinicians are often the most acquainted with constricting band syndromes. If surgical amputation is considered or desired, orthopedic surgeons would be well-equipped to address the conditions of these patients.

Deterrence and Patient Education

The spontaneous formation of a fibrous ring of tissue around the base of a toe or finger characterizes ainhum. Ainhum is frequently observed on both feet, with the fifth toe being the most common site. This condition primarily affects males of African descent within the age range of 30 to 50. The exact cause of ainhum remains unknown, although genetic predisposition is believed to be a contributing factor.

Ainhum typically follows a predictable progression, with the initial symptom being the formation of a fissure or groove on the underside of the toes. Eventually, as the fissure expands, encompassing the entire toe, the toe may become swollen due to lymphedema. Over time, the bone and blood vessels experience constriction, potentially leading to bone fractures or detachment. Ultimately, the affected toe will undergo auto-amputation or fall off.

Treatment options for ainhum are limited and primarily focus on pain management. In the early stages, locally injected corticosteroids and topical steroids or retinoids may be considered, although their effectiveness remains uncertain. Another option is using the Z-plasty technique to alleviate constriction in the early stages. During the later stages, amputation of the affected digit becomes the most viable option. As no specific behaviors have shown consistent associations with ainhum, preventative counseling is not currently feasible. In pseudoainhum or secondary ainhum cases, patients should take measures to avoid any identifiable triggers and ensure that underlying disease processes are adequately treated.

Enhancing Healthcare Team Outcomes

Ainhum is an often underrecognized disease process that highlights the importance of early identification to facilitate effective treatment. Raising awareness among the healthcare team members can potentially lead to earlier recognition of the condition, which may reduce the incidence of amputations, secondary infections, and psychological distress among affected individuals. Physical and occupational therapists can play a crucial role in enhancing the quality of life for affected individuals, complementing the symptomatic and definitive treatments offered by other healthcare professionals.

Researchers have yet to investigate the social and psychological ramifications of ainhum thoroughly. However, psychiatric professionals, psychologists, counselors, or pastoral care providers may help address the often underestimated psychological impact of this disease. Although historically more prevalent in rural areas of South America, Africa, and India, the changing migratory patterns of ainhum suggest clinicians in the Western world and developed nations may be more likely to encounter the condition. All studies about ainhum are classified at evidence level 5 or lower. Due to the rarity of the disease, well-structured clinical trials are notably lacking.