Pityriasis rosea Lianjun Chen Huashan Hospital

Definition an acute, self-limited skin disease characterized by the presence of rosy-coloured round to oval macular lesions with a rim of fine scales appear most common in crops on the trunks and proximal extremities.

Epidemiology Most cases of pityriasis rosea occur in young healthy persons, the majority of whom are between the ages of 10 and 35 years. Its peak incidence is during adolescence, and it is rarely diagnosed before the age of 2 years. There is no racial predilection and it is found worldwide. There is a slight female predominance, and some studies have even suggested a female : male ratio of 2 : 1. The typical eruption lasts 6 to 8 weeks, though exceptionally it can persist for 5 months or longer. Some authors report a modest seasonal variation with peaks in the spring and fall.

Etiology and Pathogenesis The etiology is unknown. A viral etiology is frequently proposed. There is some evidence implicating HHV6 &7 infection in the pathogenesis .

Clinical Manifestation Predominantly seen in adolescents and young adults during spring and fall. Occur mostly on the trunks and proximal extremities. Lasting for about 6-8 weeks or longer. Self-limited. Recurrences are regarded as unusual.

Clinical Manifestation The initial lesion is frequently a single, 2-5cm or bigger round plaque,names as “Herald patch”. Within several days, smaller oval maculars appear, with a wrinkled, salmon-colored central area and a darker red peripheral zone with gyrate border ,separated by a collarette of fine scaling . The lesions distribute with their long axis following Langer's lines of cleavage.

Herald patch

A self-limited papulosquamous eruption that is occasionally pruritic Seen primarily in adolescents and young adults, favoring the trunk and proximal extremities Individual lesions are usually oval in shape and their long axis is oriented along Langer's lines of cleavage Less common variants include inverse, vesicular, purpuric and pustular

Differential Diagnosis Tinea corporis nummular dermatitis Psoriasis Syphillis Seborrheic dermatitis Drug eruption

Treatment Traditional Chinese medicine ：heat-clearing and detoxicating Symptomatic treatment：antihistamines Topical corticosteroids Phototherapy A brief course of systemic corticosteroids(Rarely)