C1q Nephropathy Presenting in the Second Trimester Leading to Fetal Growth Restriction and Fetal Demise

Introduction: C1q nephropathy is a rare kidney disorder characterized by abnormal deposition of the C1q protein in the glomeruli. Clinical presentation varies widely, ranging from asymptomatic proteinuria to full-blown nephrotic syndrome with severe edema, hypoalbuminemia, and hyperlipidemia. It is diagnosed with a kidney biopsy revealing immune complex deposits with a full house immunofluorescence pattern. Pregnancy in patients with C1q nephropathy is not well studied however, general risks include worsening proteinuria, increased risk of preeclampsia, intrauterine growth restriction. Case Description: A 41-year-old gravida 1 para 0 female, who conceived through in vitro fertilization, presented at 16 weeks gestation with bilateral upper and lower extremity swelling, dyspnea and elevated blood pressure. Laboratory findings and clinical presentation were consistent with nephrotic syndrome. She was started on steroids and furosemide. Kidney biopsy revealed immune complex-mediated mesangial proliferation with nephritis, exhibiting a full-house staining pattern on immunofluorescence, consistent with C1q nephropathy. Serological markers for SLE were negative. Her pregnancy was complicated by intrauterine growth restriction and subsequent intrauterine fetal demise at 23 weeks. Discussion: C1q nephropathy typically presents in childhood or early adulthood with lower extremity edema. It is an uncommon cause of non-lupus full-house glomerulonephritis. In this case, the patient developed symptoms at age 41, with onset occurring during pregnancy. Given that lower extremity edema is common in pregnancy, the diagnosis could easily be missed. The presence of mesangial proliferation, mesangial dense deposits, full-house staining on immunofluorescence, strong positive C1q staining, and the absence of clinical symptoms of systemic lupus strongly support the diagnosis of C1q nephropathy. C1q nephropathy should be considered in all pregnant patients with lower extremity edema and proteinuria.