Hereditary progressive mucinous histiocytosis is a rare, benign, non-Langerhans cell histiocytosis characterized by childhood or adolescence onset of multiple, small, asymptomatic, slowly progressing, skin-colored to red-brown papules with predilection for the face, dorsal hands, forearms and legs, without associated mucosal or visceral involvement. Histologically, papules are well-circumscribed, unencapsulated, nodular aggregates of histiocytes with abundant mucin in the upper and middermis.

Pruritus is an itch or a sensation that makes a person want to scratch. This term refers to an abnormally increased disposition to experience pruritus.