Rapidly progressive glomerulonephritis in IgA/IgG cryoglobulinemia.

Mixed IgA/IgG cryoglobulins were found in the serum of a 48-year-old man suffering from rapidly progressive glomerulonephritis (RPGN) with crescent formation. The type-II cryoglobulins were composed of monoclonal IgA1-kappa and polyclonal IgG, with the IgA possessing antibody activity against the IgG. The RPGN was of the immune complex type with granular deposits of IgA, IgG, and C3 on immunofluorescence microscopy and preponderant subendothelial deposits on electron microscopy. Occluding protein thrombi could be demonstrated in several glomerular capillary loops. Removal of the cryoglobulins from the patient's serum by plasmapheresis and immunosuppression was paralleled by a remarkable improvement in renal function with fall of serum creatinine values from 13.6 mg/dl (1,202.2 mumol/l) to 2.8 mg/dl (247.5 mumol/l), a resolution of the glomerular lesions, and clinical improvement as well. Our observations suggest that the crescentic glomerulonephritis may be due to an immune complex-like deposition of the cryoproteins. We conclude that crescentic glomerulonephritis in IgA/IgG cryoglobulinemia has to be considered as an autoimmune form of RPGN.