Factor VIII related antigen and childhood rheumatic diseases.

Factor VIII related antigen (FVIIIRAg) levels were measured in the plasma of 63 children with rheumatic diseases and 20 controls. High levels were found in patients with systemic juvenile arthritis, systemic lupus erythematosus, dermatomyositis and systemic forms of vasculitis. The amount of circulating FVIIIRAg seemed to be independent of values for erythrocyte sedimentation rate, C-reactive protein and fibrinogen, implying that it was not just another acute phase reactant. Rather, a high level of circulating FVIIIRAg most likely reflects the presence of vascular endothelial injury, and this test may be useful in monitoring disease activity in children with rheumatic diseases in which vasculitis is present.