IgA nephropathy in a patient with ankylosing spondylitis and a solitary kidney.

We describe a patient with ankylosing spondylitis and psoriasis who was found to have IgA nephropathy in a solitary kidney. Renal biopsy demonstrated mesangial proliferation and interstitial nephritis with mesangial deposition of IgA. Although the renal disease and the rheumatic disease could have been present together by chance association, evidence is presented to suggest a possible common pathogenesis.