1. Pityriasis rosea

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

3. The etiology is unknown.Though a viral origin has often been suggested,attempts at isolating virus have been negative. Etiology and Pathogenesis

4. seen predominantly in adolescents and young adults during spring and fall 。 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 axes following the lines of cleavage of the skin. 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

6. Pityriasis rosea is distinguished from psoriasis and seborrheic dermatitis by its oval maculars, salmon- colored central area, raised 、 darker-red border and a collarette of fine white scaling 。 “Herald patch” may closely resemble tinea corporis ， sometimes,drug eruption may mimic the clinical features of pityriasis rosea,too. Diagnosis and differential diagnosis

7. treatment treatment traditional Chinese medicine ： heat- clearing and detoxicating traditional Chinese medicine ： heat- clearing and detoxicating Symptomatic treatment ： antihistamines Symptomatic treatment ： antihistamines Itching may be alleviated with antipruritics or anti-inflammatory drugs Itching may be alleviated with antipruritics or anti-inflammatory drugs