IgA. Nephropathy—A, Clinicopathologic Study—

Abstract

Thirty nine of 124 renal biopsy specimens taken from patients witn a variety of renal diseases were identified as IgA nephropathy. In 34 of the 39 specimens, morphologic and immunologic findings were studied in detail with clinical data. Most of the patients had microscopic hematuria and slight proteinuria, but renal function was almost normal. Light microscopic examination showed the findings of generalized proliferative glomerulone-phritis, but no findings of focal glomerulonephritis. The most uniform abnormality was that the intensity of the mesangial proliferation varied remarkably in different segments in a given glo-merulus, just as it differs from one glomerulus to another or from one case to another. Therefore, it is not reasonable to express the light microscopic alterations of IgA nephropathy as focal or generalized glomerulonephritis. However, it is desirable to classify them into the terms of IgA nephropathy-minimal change, IgA nephropathy-slight (mild), IgA nephropathy-moderate, and IgA nephropathy-advanced, judging from glomerular, tubulo-interstitial and arteriolar changes. In this study, morphologic features ranged from minimal change (3 patients) to advanced (2 patients). In light microscopy PAS-positive paramesangial deposits were seen in a high rate (39% of the total glomeruli and 80% of the cases) and these were rarely seen in other renal biopsy specimens. In electron microscopy the deposits were present in the mesangium, intramenbranous position and subeudothelium, but their electron-densities were various. Serum IgA values were significantly elevated. Assay of individual complement components in IgA nephropathy had shown a characteristic profile with slightly low C3 proactivator, high C4 and remarkably low C3. In immunofluorescence studies IgA was detected in 100% of the patients, IgG in 48%, IgM in 47%, IgE in 8%, Clq in 0%, C4 in 0%, properdin in 83%, C3 proactivator in 50%, C3 in 100% and fibrinogen in 50%. These evidences suggest participation of the alternate pathway at C3. However, since IgA was the only constant immunoblobulin in this study, it is preferable to employ the term IgA nephropathy for this disease rather than the term IgA-IgG mesangial nephropathy as employed by others. There was no correlation between the injury and the clinical data except the deterioration in GFR. These results may suggest that IgA nephropathy can be considered as a distinct clinicopatho-logic entity.