IgG nephropathy - confusion and overlap with C1q nephropathy

Abstract

IgG nephropathy is one of the most recently described glomerulopathies, which frequently overlaps with C1q nephropathy. To clarify this entity, we evaluated renal biopsy cases with IgG deposits as a sole or predominant immunoglobulin.

METHODS: Fourteen cases demonstrating IgG as a predominantly deposited immunoglobulin in patients without infectious or autoimmune diseases between 1997 and 2008 were studied. Twelve patients had glomerular disease in the native kidney and the other 2 were renal allograft recipients.

RESULTS: Clinical presentation was microscopic hematuria, proteinuria, or both and nephrotic syndrome was observed in 3 patients. Segmental glomerulosclerosis was observed in 4 patients and mesangial hypercellularity was present in 7. Tubulointerstitial changes were not evident except for allograft biopsies. on immunofluorescence, mesangial or capillary wall IgG deposits were present in all cases, and C1q was observed in 11 cases in a similar pattern with IgG, co-dominant in 5 cases and dominant in 1.

CONCLUSIONS: Since a significant overlap is frequently observed in these two rare conditions, we suggest a tentative diagnosis of IgG/C1q nephropathy in such cases.