Pityriasis lichenoides is a clonal T-cell disorder that may develop in response to foreign antigens (eg, infections or drugs) and may be associated with cutaneous T-cell lymphoma.
Pityriasis lichenoides has distinct acute and chronic forms, which are usually distinct entities; however, lesions may evolve from the acute to chronic type. The acute form typically appears in children and young adults, with crops of asymptomatic chickenpox-like lesions that typically resolve, often with scarring, within weeks to months. Antibiotics (eg, tetracycline, erythromycin) or phototherapy may help.
The chronic form initially manifests as flatter, reddish-brown, scaling papules that may take months or longer to resolve. No treatment has proved effective.
Last full review/revision October 2012 by Peter C. Schalock, MD