Research Article: C1q nephropathy in adults is a form of focal segmental glomerulosclerosis in terms of clinical characteristics

Date Published: April 19, 2019

Publisher: Public Library of Science

Author(s): Kipyo Kim, Hyung-Eun Son, Ji-Young Ryu, Hajeong Lee, Seung Hyeok Han, Dong-Ryeol Ryu, Jin Ho Paik, Sejoong Kim, Ki Young Na, Dong-Wan Chae, Ho Jun Chin, Se Won Oh, Paolo Cravedi.


Although C1q nephropathy (C1qN) was introduced three decades ago, the clinical significance and renal outcomes of C1qN remain unclear. This study aimed to evaluate the clinical characteristics of C1qN, including renal outcomes, by performing a matched comparison within a multicenter cohort. We enrolled 6,413 adult patients who underwent kidney biopsy between January 2000 and January 2018 at three tertiary hospitals in Korea. We compared the clinical characteristics of 23 patients with C1qN with those of patients with focal segmental glomerulosclerosis (FSGS) or minimal change disease (MCD) who were matched by age, sex, diabetic status, and a period of biopsy. Histological and clinical parameters in patients with C1qN were also evaluated according to the different pathological phenotypes. For a mean follow-up period of 92 months, 4 patients with C1qN (17.4%) developed end-stage renal disease (ESRD). None of the matched patients with MCD had ESRD, but 7 (30.4%) of patients with FSGS progressed to ESRD, which was not different from that of C1qN patients (p = 0.491). Laboratory and pathological findings, except segmental glomerulosclerosis, were not notably different between FSGS and C1qN. The presence of segmental glomerulosclerosis, mesangial hypercellularity, and podocyte effacement did not affect both the short- and long-term renal outcomes in patients with C1qN. Our study showed that the renal outcomes of C1qN are comparable with those of FSGS, and not with MCD. Specific pathological findings, including segmental glomerulosclerosis in C1qN, were not associated with renal outcomes, which may suggest homogeneity in the clinical features of C1qN.

Partial Text

C1q nephropathy (C1qN) was first proposed by Jennette and Hipp in 1985, defined as a mesangial dominant or co-dominant deposition of C1q without evidence of systemic lupus erythematosus [1]. C1qN appears to be more common in children and young adults. The prevalence of C1qN is reported to be approximately 1.9–6.0% in unselected series of renal biopsies, but in some pediatric studies, it has been reported to be as high as 16.0% [2–4]. C1qN presented with diverse clinical manifestations such as nephrotic syndrome, mild proteinuria with or without hematuria, recurrent gross hematuria, nephritic syndrome, acute kidney injury, and rapidly progressive glomerulonephritis [5–9]. The histological findings of C1qN are also known to be heterogeneous. While some authors suggested that C1qN is within the spectrum of minimal change disease/focal segmental glomerulosclerosis (MCD/FSGS), C1qN is largely classified into the following two histological variants according to the light microscopic features: podocytopathy variant, including MCD and FSGS, and mesangial proliferative glomerulonephritis (GN) variant [4, 10]. Over the past 30 years, several studies regarding the clinical characteristics, treatment, and outcome of C1qN have been published. However, whether C1qN is a distinct clinicopathological entity or is variant of other glomerular diseases is still controversial. The clinical implication of the C1qN diagnosis also needs to be evaluated.

This study showed the short- and long-term renal prognosis in C1qN, which were not related to the presence of segmental glomerulosclerosis, mesangial hypercellularity, podocyte effacement grade, and other pathological parameters. The LM findings of C1qN were not markedly different from those of FSGS, except for the amount of segmental glomerulosclerosis. Furthermore, the renal prognosis in C1qN was also not significantly different from that in FSGS.




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