Focal Segmental Glomerulosclerosis (FSGS) Progressing to Collapsing Glomerulopathy in Renal Transplant Recipients With and Without COVID-19 Infection.

BACKGROUND: Collapsing glomerulopathy (CGN) secondary to HIV or COVID-19 infection mainly occurs in patients of African American descent due to APOL-1 gene mutations, but CGN is occasionally reported in white patients. CGNs are rarely reported in renal transplant biopsies and their association with idiopathic focal segmental glomerulosclerosis (FSGS) is unclear. METHODS AND RESULTS: Patient #1 was a 48-year-old Caucasian white man who had a renal transplant 8 years ago and was recently diagnosed with COVID-19 infection. Two weeks post infection, his serum creatinine (SCr) increased to 2.01 mg/dL from a baseline of 1.40 mg/dL, and he developed concomitant nephrotic range proteinuria. The first renal transplant biopsy showed FSGS. Four weeks later, his sCr level increased to 2.65 mg/dL with worsening proteinuria, and a second renal transplant biopsy revealed CGN. Patient #2 was a 32-year-old African American man whose native renal biopsy revealed primary FSGS. He received a renal transplant with initial post-transplant sCr level at 1.17 mg/dL. Four months later, his sCr and protein-to-creatinine ratio began to rise. Sequential biopsies revealed that the patient had developed recurrent FSGS, which progressed to show features of CGN. The CGN was further confirmed in his transplant kidney graft at autopsy later. CONCLUSIONS: This is the first case report of CGN in a white renal recipient with COVID-19 infection. The pathologic presentations of FSGS progressing to collapsing FSGS in our 2 renal transplant recipients suggest that FSGS and GGN may share a common pathophysiologic mechanism of podocytopathy.