Primary focal segmental glomerulosclerosis in a patient with ankylosing spondylitis: A rare presentation requiring a broad differential in nephrotic syndrome.

Ankylosing spondylitis (AS) presents with renal failure and proteinuria in a minority of cases, usually due to secondary amyloidosis or IgA nephropathy. While focal segmental glomerulosclerosis (FSGS) is less common, it should still be in the differential regardless of the patient's clinical profile.