[Spontaneous dactylolysis or ainhum. Histopathologic study].

Ainhum or dactylolysis spontanea is characterized by the occurrence of a circular constriction located at the root of the 5th toe, rarely of a finger. It deepens, the toe becomes disabled and finally amputation occurs, spontaneously or by surgery. It is a tropical disease of the adult, the origin of which remains obscure. It seems frequent in Niger. 7 cases have been histologically studied. Classical features have been found, including hyperkeratosis, chronic dermatitis, osteoporosis with cortical bone resorption. This study has also revealed in all cases complete ligamental destruction. Moreover, vegetal foreign body granulomas have been found in 4 cases, lying deep in the dermis and in one case in a synovial membrane. Ainhum is compared with pseudo-ainhum seen in genodermatosis, in yaws and in congenital strictures. Among the usually considered etiopathogenetic hypotheses, our findings are in favor of a mechanical and inflammatory origin.