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Abstract: SA-PO264

Overlap of C3 Glomerulonephritis and Thrombotic Microangiopathy

Session Information

Category: Glomerular

  • 1005 Clinical Glomerular Disorders

Authors

  • Ravindran, Aishwarya, Mayo Clinic, Rochester, Minnesota, United States
  • Fervenza, Fernando C., Mayo Clinic, Rochester, Minnesota, United States
  • Sethi, Sanjeev, Mayo Clinic, Rochester, Minnesota, United States
Background

Dysregulation of the alternate pathway (AP) of complement underlies the pathogenesis of both C3 glomerulonephritis (C3GN) and thrombotic microangiopathies (aHUS/TMA). In this study, we describe both the disease entities occurring in a series of 5 patients.

Methods

We identified 114 patients seen at the Mayo Clinic from 2007-2016 with a diagnosis of C3 glomerulopathy (C3GN or DDD) in native kidney biopsies. Patients with tissue diagnosis of thrombotic microangiopathy along with C3G were included.

Results

The median age at diagnosis was 58 years (range: 28-69), all were male. The median serum creatinine and proteinuria at presentation were 2.2 mg/dL (range: 1.7-3.2) and 2089 mg/24 hours (range: 250-5220). Monoclonal protein was present in 1 of the 3 patients tested. None of the patients had a history of infection or autoimmune disease. Light microscopy showed a membranoproliferative GN in 3 patients and a mesangioproliferative GN in 2 patients. Immunofluorescence showed bright C3 staining in the mesangium and/or capillary walls. On electron microscopy, capillary loops showed marked subendothelial expansion by fluffy material (and absence of deposits in these loops). However, capillary wall deposits were present in other loops in 4 (80%) of 5 biopsies. Mesangial deposits were present in all the biopsies. Ultrastructural features of DDD were not present; thus all biopsies were consistent with C3GN and aHUS/TMA. Complement studies showed low C3 in 4 (80%) patients, low C4 in 2 (40%) patients. Genetic evaluation of the AP showed positive CFH mutation and polymorphisms of CFB/CFH/CFHR5 genes in 1 patient tested. One patient had normal ADAMTS13, others were not tested. Of the 5 patients, 1 recieved steroid only; 1 received steroid and mycophenolate mofetil; 1 received therapeutic plasma exchange, steroid, eculizumab, cyclophosphamide; 1 was managed conservatively, and 1 was recommended therapeutic plasma exchange but lost to follow-up. At a median final follow-up of 18.3 months (range: 4-47.2), 1 progressed to ESRD, and for the remaining, the median creatinine and proteinuria were 2.5 mg/dL (range:1.4-3.6) and 1169 mg/24 hours (range: 947-2172), respectively.

Conclusion

We describe the clinicopathological features and renal outcomes of patients with features of both C3GN and aHUS/TMA. Dysregulation of the AP of complement can result in either C3GN, aHUS/TMA, or overlapping C3GN/aHUS.