IgA nephropathy with subendothelial deposits.

IgA nephropathy with subendothelial deposits in the capillary walls of the glomeruli (IgA type 2) was compared histometrically and clinically with IgA nephropathy without subendothelial deposits (IgA type 1) and membranoproliferative glomerulonephritis with subendothelial deposits (MPGN). Study cases consisted of 32 biopsies from 26 patients of IgA type 1, 25 biopsies from 20 patients of IgA type 2 and 31 biopsies from 27 patients of MPGN. Histological changes of the glomeruli consisted of an increase in the mesangial matrix and hypercellularity in the mesangium in both types of IgA nephropathy, and the degree of the changes was a little higher in IgA type 2 than in IgA type 1 (0.02 < P < 0.05). Mesangial changes of MPGN were marked as compared with IgA type 1 and IgA type 2 (P < 0.001). Histometry of the mesangium on the cases followed up showed that the degree of mesangial thickening increased with lapse of time in IgA type 2 and MPGN, whereas it remained unchanged up to 13 years in IgA type 1. Proteinuria tended to be mild in IgA type 1, moderate in IgA type 2, and marked in MPGN. The impairment of renal function was observed in 21.9% of IgA type 1, in 36.0% of IgA type 2 and in 58.1% of MPGN. IgA type 2 has been shown to be pathologically and clinically intermediate between IgA type 1 and MPGN. These results suggest that there is a clinicopathological overlap between IgA nephropathy and MPGN with IgA deposition.