If no IgA, but IgG or IgM, is detected around vessels, this indicates another subtype of immune complex vasculitis, e.g., cryoglobulinemic vasculitis, hypocomplementaemic vasculitis (Figure 2), or systemic disease associated with IC-mediated vasculitis such as rheumatoid arthritis or vasculitis in SLE (Table 1). The gene discussed is CD40LG; the disease is systemic lupus erythematosus.