Ainhum consists in the formation of a constricting ring involving a part of or the entire circumference of a toe, at or near its base. This furrow deepens, with eventual spontaneous amputation of the portion distal to the constriction. Usually the fifth toe is involved, but any toe may be affected, and involvement is usually symmetrical. The distal portion prior to its severance becomes bulbous and hypertrophied. Progress of the constriction may cease at any point. The groove is usually located over the first interphalangeal joint; the next most frequent location is over the second phalanx. Men are most commonly affected, but it has been observed in women or children, and affected individuals are generally in good health otherwise (summary by Horwitz and Tunick, 1937).
Ainhum-like constriction bands occur with neurogenic acroosteolysis (201300) and with mutilating keratoderma (124500, 248300). [from
OMIM]