INTRODUCTION
Alkaptonuria is an autosomal recessive disease caused by a deficiency of homogentisic acid 1,2-dioxygenase that leads to homogentisic acid (HGA) accumulation. Its clinical signs include dark urine, melanin-like pigmentation of tissues (ochronosis), and ochronotic arthropathies. HGA accumulation also affects the cardiovascular system, especially the heart valves. Alkaptonuria cannot be diagnosed preoperatively since most of the clinical signs are confirmed intraoperatively.
We present a rare case of aortic valve stenosis (AS) with black pigmentation caused by alkaptonuria that was diagnosed postoperatively. Cardiac surgeons should recognize this condition when they observe typical signs during surgery.