Pityriasis lichenoides is a term used to refer to a group of rare acquired inflammatory skin disorders that includes pityriasis lichenoides chronica (PLC), pityriasis lichenoides et varioliformis acuta (PLEVA), and the febrile ulceronecrotic Mucha-Habermann disease (FUMHD) variant of PLEVA. The use of the term pityriasis lichenoides to refer to all three disorders is representative of the theory that PLC, PLEVA, and FUMHD may represent a clinical spectrum of a single disease.
PLC is clinically characterized by the development of multiple, scaly, erythematous to brown papules on the trunk and extremities. The condition usually has a relapsing and remitting course that persists for months or years.
The clinical manifestations, diagnosis, and management of PLC will be reviewed here. PLEVA is discussed separately. (See "Pityriasis lichenoides et varioliformis acuta (PLEVA)".)
Definitive conclusions on the epidemiology of pityriasis lichenoides chronica (PLC) are hindered by the frequent lack of distinction between the subtypes of pityriasis lichenoides in the published literature and limited data. In general, PLC is considered a rare disorder that is most likely to occur in young adults and children . However, PLC may develop at any age.
The existence of sex, ethnic, or racial predilections in PLC is uncertain . Based upon data from a few retrospective studies of children with pityriasis lichenoides, there may be a slight male predilection for pityriasis lichenoides in the pediatric population [3-7]. In one of the largest series of children with PLC (n = 46), 59 percent of the children were male .