C4A and non-Hodgkin lymphoma: However, in more than 20–40% of patients the disease extends beyond the exocrine glands, manifested either by epithelial lymphocytic invasion of the lung, liver or kidney or by immune complex-mediated phenomena such as skin vasculitis, peripheral neuropathy, glomerulonephritis and low serum C4 levels, all of which have previously been shown to confer increased risk for non-Hodgkin’s lymphoma (NHL) development [1–3].