Coexistence of Proteinase 3 (PR3)-Positive Granulomatosis With Polyangiitis and Genetically Confirmed Alport Syndrome in a 31-Year-Old Female Patient: A Diagnostic and Management Challenge.

Distinguishing autoimmune glomerulonephritis from hereditary nephropathy is critical to avoid unnecessary immunosuppression and ensure appropriate long-term renal monitoring. A 31-year-old Hispanic female patient with a complex medical history, including proteinase 3 (PR3)-positive granulomatosis with polyangiitis (GPA), rheumatoid arthritis, Raynaud phenomenon, seizure disorder, autism spectrum disorder, bipolar disorder with psychotic features, and cochlear implantation in childhood, was found to have genetically confirmed Alport syndrome through Natera testing (Natera, Inc., Austin, Texas, United States). Despite preserved renal function (estimated glomerular filtration rate (eGFR) 107 mL/minute/1.73m²), urinalysis demonstrated persistent proteinuria. Her history of early-onset hearing loss requiring cochlear implantation raised suspicion for hereditary nephropathy. Elevated anti-PR3 antibodies were present without clinical evidence of active vasculitis. The coexistence of autoimmune disease and hereditary collagen IV nephropathy complicated the attribution of urinary abnormalities. This case highlights the importance of genetic evaluation in patients with multisystem disease and urinary abnormalities, particularly when clinical features such as early-onset sensorineural hearing loss are present. Recognition of Alport syndrome in patients with coexisting autoimmune vasculitis has significant implications for renal surveillance, immunosuppressive stewardship, and multidisciplinary management.