C4A and hypersensitivity vasculitis: However, the patient also had typical features of mixed cryoglobulinemic vasculitis—the purpuric rash with leukocytoclastic vasculitis, C4 hypocomplementemia, elevated RF and type II cryoglobulinemia with polyclonal and monoclonal IgM components—which would also account for positive IgM and C3 staining on immunofluorescence studies.