Cryoglobulinemic glomerulonephritis (GN) is caused by intracapillary, capillary wall (often subendothelial), and mesangial cryoglobulin deposits, giving a membranoproliferative pattern of injury. Patients have nephritic/nephrotic syndrome with various levels of kidney function. Purpura and arthralgia occur in about one-third, with vasculitis affecting skin and kidneys less commonly. Abnormal serologic studies include low C4 in three-quarters and low C3 in half. All 3 types of cryoglobulins, including those due to both monoclonal and polyclonal immunoglobulins, can cause cryoglobulinemic GN, although most commonly it occurs in settings of type II (“mixed”) cryoglobulinemia secondary to hepatitis C virus (HCV) infection.