Collapsing Focal Segmental Glomerulosclerosis (cFSGS) and Its Association with Influenza A and Positive Cytoplasmic ANCA (C-ANCA) Serology: A Case Report

Introduction: Collapsing FSGS is aggressive variant of glomerular diseases characterized by a rapid decline in renal function and poor prognosis. This report contribute to the existing literature by presenting a case of cFSGS associated with influenza A infection and positive C-ANCA. Case Description: A 35-year-old male presented with flank pain preceded by upper respiratory tract infection symptoms. Physical examination was unrevealing. Laboratory findings were significant for creatinine of 1013 umol/L, albumin of 28 g/L. Urine studies showed microscopic hematuria, 24 hours urine collection was 300 ml with 2 g of proteins. He tested positive for influenza A. He was admitted and started on pulse steroid. Serology revealed high C-ANCA titer. Renal biopsy showed cFSGS as described in figure 1. He required hemodialysis for refractory hyperkalemia. He was discharged with tapering dose of steroids and hemodialysis twice weekly that was stopped few weeks later. After 6 months, his labs showed stable creatinine with GFR of 27, reduction in proteinuria, and normal serum albumin. Discussion: The exact etiology of cFSGS is unknown. Several reports highlighted the association with various viral infections. In our case, influenza A virus appeared to have a crucial role in triggering cFSGS. The presentation of rapid decline in renal function, microscopic hematuria and positive C-ANCA may lead to incorrect initial diagnosis of rapidly progressive glomerulonephritis thus signifying the importance of confirming diagnosis with renal biopsy before commencing the patient on aggressive immunosuppressive therapy. Overall, the association between cFSGS, influenza A infection, and positive C ANCA serology suggests a complex interplay between viral triggers, and immune dysregulation.Figure 1: Segmental collapse of glomerular tufts, acute tubular injury and mild interstitial fibrosis and tubular atrophy