Glomerulonephritis with mesangial deposits of IgA unassociated with systemic disease.

Typical features of IgA-associated nephritis were found in renal biopsies from 16 of 355 consecutive patients. Generalized segmental mesangial proliferation was noted in biopsies from most patients, and dense deposits were detected by electron microscopy in mesangial regions of approximately 50% of biopsies. Immunofluorescent studies showed IgA to be the predominant immunoglobulin in glomueruli; IgG was present in less than 50% of biopsies and IgM in only 12%. The serum IgA value was significantly increased (P les than 0.001) in 50% of patients and the mean IgA/IgG ratio was significantly increase (P less than 0.001) for the patient group as a whole, which suggests a selective increase in IgA. Mesangial deposits of C3 were present in 15 of 16 biopsies and properdin was noted in all biopsies tested; C4 was not demonstrated in any biopsy. This suggests activation of the alternative complement pathway. The results of this study support the concept that IgA-associated nephritis is a unique condition that in some patients gives rise to idiopathic recurrent hematuria. Although the prognosis is good in the majority of patients, the renal disease may progress.