Which rashes are specific to causes of juvenile arthritis?
Erythema marginatum is a nonpruritic macular rash with a serpiginous erythematous border. The rash is pathognomonic of acute rheumatic fever and is one of the five major criteria. It appears in the acute phase of illness along with carditis and arthritis and may remain for many weeks thereafter.
Lower extremity purpura is characteristic of IgA vasculitis (Henoch–Schönlein purpura). It appears in crops, ranging from small petechiae to large ecchymoses. This rash is seen several days before other common manifestations of joint swelling and abdominal pain. It follows a self-limited course, with resolution by 4 weeks for most children.
Evanescent salmon pink macules are seen in 80% of patients with sJIA. The rash coincides with febrile episodes and disappears within a few hours without residua. It is migratory, commonly appearing on the trunk and extremities. Small macules are often surrounded by pallor, whereas larger macules have central clearing. In older patients, the rash appears more urticarial and may be pruritic. Individual lesions may be elicited by rubbing or scratching the skin (Koebner phenomena) or by heat (hot bath or a warm washcloth rested on the skin)
