Pityriasis Lichenoides Chronica

Pityriasis lichenoides chronica (PLC) (also known as "Chronic guttate parapsoriasis," "Chronic pityriasis lichenoides," "Dermatitis psoriasiformis nodularis," "Parapsoriasis chronica," and "Parapsoriasis lichenoides chronica") is an uncommon, idiopathic, acquired dermatosis, characterized by evolving groups of erythematous, scaly papules that may persist for months. It is of unknown etiology. Uncertainty about the etiopathogenesis of this skin disease is the reason for the unpredictable and non optimal efficacy of therapies available for its treatment.

PLC is a benign eruption with lymphocytic infiltrates of the skin, presents as a persistent, erythematous, papular eruption with scale. Patients may have guttate, hypopigmented macules with scale in addition to papules.

PLC is thought by some investigators to represent a hypersensitive reaction to an infectious agent since there are reports of clustering of cases and familial outbreaks.  PLC has been reported in association with human immunodeficiency virus (HIV) infection  and improves with rise in CD4 count. Epstein-Barr virus (EBV) has been associated with PLEVA and PLC outbreaks which resolved with resolution of the EBV. Toxoplasma gondii  was reported in PLC in 1972 in six of eleven patients. Other infectious agents that have been implicated as causing PLC include adenovirus and parvovirus B19.

All races are affected. A racial predisposition has not been reported.

A male predominance has been reported in the pediatric population and in patients presenting with febrile ulceronecrotic Mucha-Habermann disease.

Most patients present during the first 3 decades of life. Studies of children have shown a variable age of onset from 3-15 years, with a mean age of 9.3 years.

Currently there is no standard of treatment for PLC.