Immunologic mechanisms in systemic vasculitis.

Thirty-four patients with systemic vasculitis were studied to determine the possible type and frequency of associated immunologic abnormalities. The patients were divided into three clinical groups--those with systemic vasculitis without respiratory tract involvement, those with systemic vasculitis with respiratory tract involvement (particularly Churg-Strauss vasculitis and Wegener's granulomatosis), and those with limited vasculitis without visceral involvement. A diminished level of serum complement was found in half the patients with systemic vasculitis without respiratory tract involvement. These patients usually had diffuse skin disease that often was associated with the presence of rheumatoid factor and cryoglobulinemia and most likely represented an immune-complex induced disease. The serum IgE often was elevated in patients who had systemic vasculitis with respiratory tract involvement, particularly those with Churg-Strauss vasculitis and Wegener's granulomatosis, and may be a clue to the pathogenesis in this group of patients.