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Abstract: PO1558

Pregnancy-Associated Membranoproliferative Glomerulonephritis (MPGN)

Session Information

Category: Glomerular Diseases

  • 1203 Glomerular Diseases: Clinical, Outcomes, and Trials

Authors

  • Vasquez Buitron, Pamela Catalina, University of New Mexico School of Medicine, Albuquerque, New Mexico, United States
  • Shaffi, Saeed Kamran, University of New Mexico School of Medicine, Albuquerque, New Mexico, United States
  • Xu, Zhi, University of New Mexico School of Medicine, Albuquerque, New Mexico, United States
  • Kuperman, Michael Benjamin, Arkana Laboratories, Little Rock, Arkansas, United States
  • Teixeira, J Pedro, University of New Mexico School of Medicine, Albuquerque, New Mexico, United States
Introduction

Nephrotic syndrome (NS) in pregnancy is rarely due to MPGN. We present a case of MPGN in pregnancy for which no other cause was found.

Case Description

A 33-year-old G1P0 woman develops hypertension and proteinuria at 12 weeks gestation followed at 21 weeks by NS (7.5g/24h proteinuria, albumin 1.1 g/dL), AKI with creatinine (Cr) 1.1 mg/dL (up from 0.6), hematuria, and mildly elevated AST and ALT. C4 is low (5.9 mg/dL). SPEP and UPEP detect monoclonal IgG kappa with serum light chain ratio 5.1. ANA, anti-dsDNA, cryoglobulins, C3 nephritic factor, and serologies for hepatitis B and C, T. pallidum, and HIV are negative. Renal biopsy [figure] reveals MPGN. After counseling, she opts to end the pregnancy. Cr, AST, ALT, and hematuria rapidly normalize, but the proteinuria at first persists. Immunosuppression is offered, but she declines. The proteinuria slowly falls to <0.7 g/g Cr with supportive care and telmisartan over a year. Apart from low C4, an atypical hemolytic uremic syndrome (aHUS) panel is negative. Genetic testing for aHUS is also negative (heterozygous mutation in DGKE and heterozygous deletion in CFH R1-CFH R3). HLA analysis shows B35 and B51 alleles. C4d staining later performed on the biopsy is strongly positive.

Discussion

As in this case, NS in pregnancy is associated with an increased risk of complications such as superimposed preeclampsia. The etiology of this MPGN case is unknown, with no clear infectious or autoimmune cause. The C4d deposition and negative aHUS testing suggest a defect in the classic complement pathway. The paraprotein may or may not be involved as, though the immune complex deposition was polyclonal, monoclonal IgG-kappa has been rarely reported to activate complement in other autoimmune disorders. Regardless of mechanism, we speculate this MPGN case was triggered by pregnancy as it improved after the pregnancy with supportive care alone.

Biopsy yielded 20 glomeruli, with mesangial and endocapillary hypercellularity (A, PAS stain), mild tubular injury, and minimal fibrosis/glomerular sclerosis. Silver stain (B) showed diffusely thickened capillary walls with double contours. IF (C) was positive for IgG, IgM, kappa, and lambda.