Nephropathy caused by non-amyloid organized and granular deposits as multiple myeloma syndrome

A rare variant of nephropathy in multiple myeloma (MM) is reported. Nephropathy is characterized basing on the study of nephrobiopsy with light, immunofluorescent and electron microscopy. A repeat biopsy of the kidney was made after achievement of a complete clinicohematological remission. A MM patient's nephrobiopsy in a picture of glomerulonephritis had 3 types of deposits: granular, irregular fibrils of 12 nm in diameter and microtubes organized in bunches 19 nm in diameter. Congo red test was negative, cryoglobulinemia was absent. Immunofluorescent test detected deposit of monoclonal IgG in the mesangium and glomerular basal membrane (GBM) corresponding to monoclonal type of monoclonal secretion. After treatment and achievement of remission, neither IgG no light chains were found in nephrobiopsy. Electron microscopy registered complete resorption of granular deposits and microtubes with formation of electron-transparent cavities. However, fibrils seen before treatment only in mesangium appeared in the above hollow cavities. The presence of such fibrils in the mesangium and GBM did not influence clinical picture of the disease. After achievement of remission the patient had no clinical and laboratory signs of nephropathy, only insignificant selective glomerular proteinurea was observed (0,5 g/l). Thus, granular deposits and microtubes contained paraprotein, they were completely resorbed after achievement of MM remission. Fibrils seem to have another genesis unrelated to monoclonal gammapathy.

multiple myeloma, fibrillar glomerulonephritis, immunotactoid nephropathy, deposits of monoclonal immunoglobulins, nephropathy