Histamine-triggered localized vasculitis in patients with seropositive rheumatoid arthritis.

To gain some insight into the pathogenesis of vasculitis in rheumatoid arthritis, and to investigate its relation to circulating immunoreactants, we injected 50 microliters of histamine intradermally in four seropositive and four seronegative patients with rheumatoid arthritis. Skin biopsies obtained before histamine and at 4 hours after histamine were studied by immunofluorescence microscopy, and skin biopsies 24 hours after histamine were studied by light microscopy. At 4 hours after histamine, all seropositive patients demonstrated deposits of IgM and complement components in dermal vessels; by 24 hours, various degrees of leukocytoclastic vasculitis were noted. Circulating material reactive with Raji cells, C1q, or both, was present in 3/3 seropositive patients. In contrast, none of the seronegative patients exhibited vascular deposits of immunoreactants or vasculitis. The results indicate that patients with rheumatoid arthritis who are seropositive may have circulating complexes with appropriate characteristics to induce vasculitis and that vasoactive substances may be used to trigger their local deposition in vessels.