Alkaptonuria, a rare metabolic disease, is caused by a genetic deficiency of the homogentisic acid oxidase enzyme involved in phenylalanine and tyrosine metabolism. Ochronotic arthropathy and cardiovascular involvement, which manifests itself in 4-6 decades as a result of homogentisic acid accumulation in cartilage and connective tissue, are the most important causes of mortality and morbidity. We present a 75-year-old case with a diagnosis of severe aortic stenosis who was diagnosed with alkaptonuria after the operation. Severe calcification and pigmentation were observed in the patient's aortic valve leaflets and at the ascending aortic wall