IgA nephropathy.

This presentation attempts to define the criteria for diagnosis of the suggested clinicopathologic entity of IgA nephropathy. Of 250 patients in whom renal biopsies with immunofluorescence, light and electron microscopic, and clinical data were available, 12 patients (4.8 per cent) showed predominance of IgA with localization mainly in the mesangium, a variable degree of mesangial cell proliferation, and increased mesangial matrix on light microscopy. Electron densities were restricted to the mesangium and paramesangial areas. IgA was accompanied by C3 only in two patients, by IgG and C3 in five, and by IgG, IgM, and C3 in five. Properdin was found in 11 of these 12 cases. There was a marked male predominance. All showed gross or microscopic hematuria and variable proteinuria. Ten had had normal renal function tests at the time of presentation, and there was no significant worsening of renal function in the 11 patients followed for six to 84 months after biopsy. No morphologic change was detected in two repeat biopsies six and seven years after the initial biopsies. These 12 patients appear to form a distinct clinicopathologic entity. They can only be separated from other glomerular disorders with IgA when the morphologic and clinical findings are considered in combination with the finding of diffuse IgA predominance on renal biopsy.