The pathology of mesangial IgA nephritis with clinical correlation

Abstract

Of 710 patients in whom renal biopsies with immunofluorescence, light microscopic, EM and clinical data were available, 239 had idiopathic mesangial IgA nephritis. In these 239 cases IgA was found alone in 45.7%, accompanied by IgG in 50.1%, IgM in 21.4%, C3 [complement component 3] in 82.4% and fibrin in 37.2%. Serum Ig levels including IgA were not significantly raised, and C3 activation was via the alternative pathway. There was a wide range of glomerular lesions with minor change, minor change with focal and segmental lesions including sclerosis and mesangial cell hypercellularity, diffuse mesangial cell proliferation and, infrequently, diffuse sclerosing glomerulonephritis. The gomerular lesions were related to the stage, duration and severity of the disease. There was also a wide variability of clinical presentations, with asymptomatic and symptomatic microscopic hematuria-proteinuria, macroscopic hematuria, recurrent proteinuria, nephrotic syndrome, acute nephritis, hypertension and uncommonly as acute renal failure and K-losing nephritis. No etiological agent was found, and both the streptococcus and HBsAg [hepatitis B surface antigen] could not be identified. The disease(s) was the commonest type of primary glomerulonephritis (33.7%) in Singapore, where this lesion has an apparent high incidence.