C1q Nephropathy: A Distinct Pathologic Entity

ABSTRACT

BACKGROUND: C1q nephropathy (C1qN) is a controversial diagnostic entity defined by Jennette and Hipp in 1985. The prevalence is very low and a few large scale studies have been reported. Application of the criteria for clinical diagnostics of C1qN may cause confusion with other glomerulonephropathies, such as minimal change disease (MCD) or focal segmental glomerulosclerosis (FSGS). In order to clarify the confusion with glomerulonephropathies, we did this study to identify the clinicopathological characteristics and the exact disease entity of C1qN. METHODS: A total of 5,258 kidney biopsies at Kangnam St Mary's Hospital were reviewed. Twenty three cases (0.44%) met the criteria of C1qN. Twenty eight cases showing dominant C1q deposits without electron dense depostis (EDD) grouped as C1q+EDD-, and previously diagnosed typical cases of MCD and FSGS were selected for this study. Four groups were compared to each other with regard to the clinical and pathological aspects of the disease. RESULTS: C1qN patients had an average age of 30.4 years. Eighteen were males and 5 were females. Eighty seven percent had proteinuria and 18% had hematuria. By electron microscopy analysis, 100% had mesangial EDD and 47.8% showed foot process effacement. C1qN had some significant differences compared with C1q+EDD-, MCD and FSGS. CONCLUSIONS: C1qN is clinically and morphologically different from MCD and FSGS. However, additional long term studies are needed to fully define C1qN from other glomerulonephritis with C1q deposits.