Dermatologic manifestations of Schistosomiasis mansoni.

Schistosomiasis mansoni, a potentially severe disease that victimizes an appreciable number of US citizens in this hemisphere, shows cutaneous changes corresponding to various stages in the life cycle of the causative parasite within its definitive host. A transient pruritus or dermatitis, probably irritative, characterizes the stage of cercarial penetration. Urticaria, periorbital edema, and rarely a purpuric eruption may occur four to six weeks later, shortly after oviposition by adult worms, probably as an expression of hypersensitivity to ova and their products. Papulonodular lesions, similar to but not as devasting as those developing internally, may rarely appear months later at the perineum or distant cutaneous sites as a manifestation of granulomatous hypersensitivity to eggs and, very rarely, worms, accidentally carried there through collateral and anastomosing vascular pathways.