Collapsing Variant of FSGS Triggered by Parvovirus B19: A Pathogenic Nexus of Viral Nephropathy and Podocyte Injury

Introduction: Focal segmental glomerular sclerosis (FSGS) is a histological lesion characterized by sclerosis in sections of some glomeruli in association with podocyte injury. Collapsing glomerulopathy correspond to a special variant of FSGS. Histologically, the collapsing form of FSGS (cFSGS) is characterized by segmental or global condensation and obliteration of glomerular capillaries, hyperplastic and hypertrophic podocytes and severe tubulointerstitial damage. Clinically, cFSGS patients present with acute kidney injury, nephrotic-range proteinuria and are at a high risk of rapid progression to irreversible kidney failure. cFSGS can be attributed to viral infections like HIV, cytomegalovirus, Epstein–Barr-Virus, and parvovirus B19. Presenting a case report of patient with Parvovirus B19 antibody positive with kidney biopsy proven collapsing type of FSGS. Case Description: 29-year-old African American male with history of Diabetes Mellitus evaluated due to worsening lower extremity leg swelling and fatigue. Physical examination pertinent for bilateral lower extremities edema and elevated blood pressure. Laboratory results impaired renal function with increasing creatinine and BUN. Further evaluation shows urine protein/ creatinine ratio over 11.4 g. ANA test negative, Hepatitis virus A, B,C and HIV ½ Ag/Ab non-reactive. Kappa Lambda ratio was normal and non-monoclonal protein was detected. GMB antibody ,Proteinase 3 and MPO antibody negative. Parvovirus B19 IgM and IgG positive suggested recent infection. Due to a massive proteinuria, renal biopsy was performed and retraction of tuft, closing of loops' lumina and hypertrophy of overlying epithelial cells is present in one glomerulus. Ultrastructural examination shows widespread effacement of podocyte foot processes. Final diagnosis consistent with focal segmental glomerulosclerosis with collapsing feature. Discussion: FSGS has been described because of parvovirus B19 infection. The collapsing FSGS is rare. African Americans are hyperproducers of transforming growth factor B, which could contribute to excessive proliferative and sclerosing in response to a viral insult. Our patient was initiate with ACE inhibitors and sodium-glucose cotransporter 2 inhibitors, and clinical improvement as the parvovirus B19 infection resolved was observed.