Pityriasis rosea describes an acute, self-limiting rash which tends to affect young adults. The aetiology is not fully understood but is thought that herpes hominis virus 7 (HHV-7) may play a role.

Features

• in the majority of patients there is no prodrome, but a minority may give a history of a recent viral infection
• herald patch (usually on trunk)
• followed by erythematous, oval, scaly patches which follow a characteristic distribution with the longitudinal diameters of the oval lesions running parallel to the line of Langer. This may produce a 'fir-tree' appearance

Management

• self-limiting - usually disappears after 6-12 weeks