= DACTYLOLYSIS SPONTANEA

[ainhum, Brazilian tribal language = fissure, saw, sword]

Etiology: unknown

Histo: hyperkeratotic epidermis with fibrotic thickening of collagen bundles below; chronic lymphocytic inflammatory reaction may be present; arterial walls may be thickened with narrowed vessel lumina

Frequency: up to 2%

Age: usually in males in 4^th + 5^th decades; Blacks (West Africa) + their American descendants; M >F

• deep soft-tissue groove forming on medial aspect of plantar surface of proximal phalanx with edema distally
• painful ulceration may develop

Location: mostly 5^th / 4^th toe (rarely finger); near interphalangeal joint; mostly bilateral

• sharply demarcated progressive bone resorption of distal / middle phalanx with tapering of proximal phalanx to complete autoamputation (after an average of 5 years)
• osteoporosis

Rx: early surgical resection of groove with Z-plasty

DDx:

1. Neuropathic disorders (diabetes, leprosy, syphilis)
2. Trauma (burns, frostbite)
3. Acroosteolysis from inflammatory arthritis, infection, polyvinyl chloride exposure
4. Congenitally constricting bands in amniotic band syndrome