Nephrotic syndrome with diffuse mesangial IgM deposits.

The renal biopsies of three cases of nephrotic syndrome were examined by light, electron and immunofluorescent microscopy. The histological appearances were characterized by mild mesangial proliferation and extensive diffuse and global deposition of IgM in the mesangial areas, with some in the capillary walls. C3 and C1q were also identified in two of the cases. Electron microscopy revealed scanty electron dense deposits in the mesangial areas and subendothelial spaces. All three patients had a nephrotic proteinuria but no hematuria. None had hypertension or renal dysfunction throughout their clinical courses. They received steroid therapy and achieved complete remission within one month after the initial treatment. Two of them, however, have had frequent relapses whenever the dosage of steroid was gradually reduced. One case continues to be free of proteinuria. These cases indicate that a distinct disease may exist, because of the uniform immunofluorescent findings. We wish to designate it as IgM nephropathy.