Ainhum, also known by the name dactylolysis spontanea, is a disease of constricting fibrous bands and possible resultant auto amputation. Historically, ainhum is a rare condition that has occurred most frequently in those of African males. The name “ainhum” is thought to have a meaning similar to a fissure from early published Brazilian reports or maybe from an Africa meaning “to saw or cut.”
Ainhum, by definition, is a constricting band disease without an identifiable cause. If a secondary cause is identified, whether a systemic condition or trauma, the disease would be classified as pseudoainhum. Unfortunately, in the absence of an underlying trigger, the pathophysiology of the progressive constricting fibrous bands is not understood.
Ainhum has a prevalence worldwide but is most common in African countries. Despite this, the prevalence may be as low as 0.015 of the population of African countries. In Brazil, another endemic area has a higher incidence in individuals with lighter phenotypes due to historical interracial marriages and offspring.
The cause of ainhum is not known. By definition, “true ainhum” must be idiopathic. This etiology is the differentiating feature from various forms of pseudoainhum which may be congenital, late-onset, or secondary to trauma. The common relationship between constricting bands of the feet and rural areas of Africa and South America has led to speculation about the trauma of walking barefoot in tropical regions.
Although biopsies are usually unnecessary to establish a diagnosis, if done, findings reveal dermal fibrosis with longitudinally oriented connective tissue. Electron micrographic findings reveal findings similar to keloidal tissue.
Clinically, the main feature is the progressive development of a circumscribed fibrotic ring at the base of the toes, or less frequently, the fingers. The most common location occurs over the fifth toe and may be bilateral.
A fibrotic band classically begins within a flexural groove. The lesion is circumferential and often slowly progresses with resultant changes distal to the constriction. Clinical criteria include three findings:
The disease may manifest through four clinical stages that are visible with radiography. First, a small callus develops and transforms into a circumferential groove or fissure. Next, the portion distant to the band becomes bulbous or globular secondary to impaired lymph and venous drainage with arterial narrowing. The third stage is typified by pain as the bone becomes separated in an intra-osseous or intra-articular location. The last stage is that of bloodless, spontaneous, auto-amputation. As the initial stage is non-specific diagnosis usually arouses clinical suspicion after the formation of the constricting band.
Although primarily a clinical diagnosis, radiography can be useful to identify the extent of disease. Also, ainhum has correlations with progressive features that may be identifiable with plain films, ultrasound, computed tomography, or even magnetic resonance imaging. The earliest phase demonstrates a deep sulcus along with the soft tissue of the phalanx; this has been likened to having the appearance of a “sand-glass.” The second phase occurs as a result of lymphedema and appears as increased volume distal to the constricting band. The third phase corresponds with the presence of bone resorption distal to the band, and the fourth phase is that of spontaneous amputation.
There has as yet been no consistent treatment established for ainhum. As the inciting event is often unidentified, there are no targeted therapies to date. In early lesions, there have been attempts made with topical and injectable corticosteroids, retinoids, or salicylates. Reports exist of a case of pseudoainhum secondary to psoriasis responding to topical pimecrolimus, and low-dose narrowband UVB. However, extrapolation of this to idiopathic ainhum seems unlikely as this patient responded to treatment of the underlying causal condition. Treatment of the constricting rings of fibrous tissue in stage-I and early stage-II disease may be treated similarly to scars and contractures. Resection of the band with subsequent z-plasty may prevent progression if performed early. Once stage-III and stage-IV disease have developed, surgical amputation or allowance for auto-amputation are the expected outcomes.
Dactylolysis spontanea often progresses over time, and spontaneous amputation occurs fur to six years after the disease onset.
After amputation of the digit(s) occur, complications may include pain, secondary infection and locomotor imbalance may occur.
Although not specifically reported, there are clinicians of the opinion that patients with ainhum or other constricting band syndromes would likely benefit from physical and occupational therapy. In patients with early disease, occupational therapy may improve mobility or even promote fine motor function after amputation has occurred. In patients with surgical or spontaneous amputation of the digits of the foot physical therapy or custom, orthotics would likely benefit patients with locomotor dysfunction and balance.
As the diagnosis is clinical, dermatologists are often the most acquainted with the constricting band syndromes. If surgical amputation is desired or is a consideration, orthopedic surgeons would also be well adapted to manage these patients.
As no distinct behaviors have demonstrated consistent links to ainhum, preventative counseling is not feasible. If psuedoainhum or secondary ainhum occurs, patients should avoid any identifiable triggers and underlying disease processes treated.
Ainhum is a disease process which is often under-recognized and may not be caught early enough to implicate effective treatment. As nurses, medical assistants, and non-physician healthcare members are often the first to see patients in the social and medical setting, increasing awareness in this community may prompt patients to seek care before symptoms occur. In addition to the physician’s interpretation of diagnostic studies and ultimate surgical treatment, physical therapists and occupational therapists can help maximize an affected individuals quality of life. Researchers have not explored the social and mental effects of ainhum, but psychiatrists, psychologists, counselors, or pastoral care may help alleviate underappreciated psychological consequences of this disease.
Although historically a disease of rural South America, Africa, and India, as migratory patterns continue to change physicians in the western world and developed nations may be more likely to encounter ainhum.
All studies at this time are evidence level V or lower. As the disease is so infrequently encountered, there have been no well-organized trials performed.
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