Description, Causes and Risk Factors:
Ainhum is the progressive constriction of the base of the fifth toe followed by spontaneous amputation. The disease is observed throughout Africa with varying frequency, in mulattos in the Antilles and South America and sporadically in other parts of the world. It is a disease of adults. The etiology and pathogenesis have not been established yet. There is some hereditary predisposition and small wounds may play a role, together with the tendency to keloid formation.
The etiology of ainhum is not fully understood. Numerous theories have been advanced from time to time but none offer a satisfactory explanation for all cases. The leprosy theory, advanced by Zambaco Pacha, and others, has been abandoned since leprosy affects white and colored alike, whereas ainhum affects the colored races almost exclusively. Bacteriologic and histologic studies have found no evidence of leprosy. Syphilis has been present only in a minority of the cases. Infections and parasites as the Chigre would not affect the dark-skinned races exclusively. To call it an annular scleroderma merely begs the question of etiology and ignores the racial factor. The term trophoneurosis does the same.
Ainhum also may have a genetic component, since ainhum has been reported to occur within families. Infection and walking barefoot in childhood are linked to ainhum but probably are not major factors in its development. Abnormal scarring does not appear to be a cause; ainhum and keloid formation rarely occur in the same individual.
Ainhum has been reported to affect all races but occurs predominately in blacks. No racial predilection exists for pseudoainhum.
Approximately 500-600 cases have been reported in the United States, but only 15 cases have been reported since 1960.
The symptoms of ainhum are purely local. There are no constitutionalsymptoms. The disease is characterized by the formation of a fissure or partial circular constriction in the skin beginning usually at the fifth digitoplantarfold on the inferior medial aspect. A warty soft corn is described as sometimes being present at the onset of the disease. The fissure or furrowmay appear on one fifth toe, the other remaining normal or becoming involvedlater, or it may appear simultaneously in both toes. Symmetry is the rule.The fissure deepens, spreads laterally and dorsally until the two wings connecton the dorsum of the foot. The toe eventually becomes completely encircledand the furrow becomes deeper and narrower as if a tight rubber band orligature had been placed around it. This process continues until the toe remains attached by a mere slender pedicle. The bone, too, is constricted andmay fracture.
The radiographic manifestations of ainhum are diagnostic.Initially, a radiolucent band can be observed constricting the base of the involved toe, with distal swelling.Osteolysis develops in the distal and middle phalanges, with a characteristic tapering effect.Ultimately, the bone narrows until it fractures and autoamputates.The radiographic appearances in pseudoainhum are similar or identical to true ainhum.
Histologically, ainhum shows fissuring and epidermal hyperkeratosis and parakeratosis, which is followed by a fibrotic reaction under the deepening fissure. The fibrosis is predominately composed of collagen. As scar tissue contracts, it constricts and narrows neurovascular bundles. Histologic appearances in pseudoainhum are similar or identical to those observed in true ainhum.
Amputation is the only effective treatment, although local injection of corticosteroids into the fibrous band reduces the pain in the rare cases where this is necessary. The treatment is focused on immediately finding and removing the constricting fiber. Surgical exploration is necessary if complete removal cannot be verified. Most cases involving the toes are caused by hair, whereas most cases involving the fingers are caused by thread from mittens. A few cases of labial or penile strangulation were noted, providing yet another reason for physicians to routinely check the diapers of their pediatric patients.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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