A germline mutation in the platelet-derived growth factor receptor beta gene may be implicated in hereditary progressive mucinous histiocytosis.

Hereditary progressive mucinous histiocytosis (HPMH) is a rare, benign, non-Langerhans' cell histiocytosis limited to skin, with autosomal dominant inheritance. The disease was first described in 1988 and 18 cases from 7 different countries have been reported to date. Clinically, HPMH is characterised by red-brown papules on the face, hands, forearms and legs and usually develops in childhood or early adolescence; lesions do not tend to regress with age (Fig. 1a).