Progressive Renal Dysfunction in Autosomal-dominant Alport Syndrome Co-occurring with C1q Nephropathy.

A 47-year-old man with nephrotic syndrome and stage 4 chronic kidney disease was diagnosed with C1q nephropathy presenting with focal segmental glomerulosclerosis (FSGS) on a renal biopsy. A genetic analysis performed because of a family history of microscopic hematuria and lamellar glomerular basement membranes identified a heterozygous COL4A4 variant, leading to a genetic diagnosis of autosomal-dominant Alport syndrome (ADAS). Despite immunosuppressive therapy, the patient progressed to end-stage kidney disease much earlier than in previously reported cases of C1q nephropathy. This case suggests that the synergistic effects of C1q nephropathy-induced podocyte damage and abnormal glomerular basement membrane due to ADAS may promote rapid progression of FSGS.