IgA-positive Versus IgA-negative Immune Complex Vasculitis

Cutaneous vasculitis due to vascular deposition of large circulating immune complexes is a disease frequently seen by general practitioners and dermatologists. The clinical symptom is palpable purpura with predilection for the lower legs. In some cases vasculitis also affects systemic organs, such as the kidneys and the intestine. When the immune complexes contain immunoglobulin class A (IgA) and when there is systemic involvement, the disease has been referred to as Henoch Schönlein purpura. When there are no signs of systemic involvement, the disease has been referred to as cutaneous leukocytoclastic angiitis. The investigators hypothesize that palpable purpura with predilection for lower legs is a pathognomonic clinical sign for immune complex vasculitis in both IgA vasculitis and IgA-negative vasculitis, but that only the presence of IgA in immune complexes is likely to be associated with systemic involvement and therefore warrants more extensive diagnostic procedures Vice versa the investigators postulate that the presence of IgG or IgM without IgA in immune complexes excludes systemic involvement The investigators also want to investigate to which of the 2 groups patients with palpable purpura and negative immunofluorescence should be assigned.