Glomerulonephritis with various crystalline deposits

A 60-year-old Japanese male was admitted with nephrotic syndrome complaining of facial and pedal edema. Renal biopsy revealed mesangial and endocapillary proliferation with massive mesangial and subendothelial deposits. Deposits of IgA, IgG, IgM, C3 and fibrinogen were identified by immunofluorescence technique in both mesangial and subendothelial areas. Deposits of kappa and lambda light chains were also recognized in similar patterns. Electron microscopy revealed crystalline structures of various appearance in these deposits. A large deposit consisted of various small triangular, quadrilateral and polygonal shapes of deposits with crystalline structures. These crystalline structures exhibited lattice or parallel lamellar lines with different periodic distances. Although a disease producing paraproteinemia was suspected, no immunoglobulin disorder or light chain abnormality could be detected on clinical and laboratory examinations. On the second biopsy, a faint reaction for cryoglobulin was recognized. However, the crystalline deposits observed in this case were absolutely different from the tubular structures seen in cryoglobulinemic nephropathy. This was a very rare and unclassified case.