IgG-associated primary glomerulonephritis in children.

Ten children with IgG-associated primary diffuse mesangial proliferative glomerulonephritis are presented. All cases showed diffuse global IgG deposits in the mesangium. IgG was the sole immunoglobulin deposited in the mesangium in 8 patients and was the predominant immunoglobulin in 2. C3 was also present in 8 patients. Light microscopy revealed variable diffuse and global mesangial proliferation in all cases, with additional focal segmental glomerular sclerosis in one. On electron microscopy, electron-dense deposits in the mesangium were identified in all patients. Clinically, 4 patients presented with the steroid-resistant nephrotic syndrome, and 6 had proteinuria and hematuria. At the latest follow-up, renal function was normal in all patients, 6 showed clinical remission and 4 had slight proteinuria and/or hematuria. These data suggest that there is a clinicopathologic entity, IgG-associated glomerulonephritis, characterized by diffuse mesangial proliferation, predominant mesangial IgG deposition, variable clinical presentation, and a relatively benign course.