text: Case History {#ccr3710-sec-0001}
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  The case of patient with aortic stenosis due to ochronosis is presented. A 63‐year‐old man with known history of alkaptonuria presented with critical aortic stenosis. His medical history included a prosthetic total hip replacement and cervical spondylosis due to degenerative arthritis (Fig. [1](#ccr3710-fig-0001){ref-type="fig"}). Physical examination showed bluish black pigmentation of the face. At operation, a severely calcified tricuspid aortic valve was observed with bluish black pigmentation involving the entire luminal surface of the ascending aorta (Fig. [2](#ccr3710-fig-0002){ref-type="fig"}A). Prosthetic aortic valve replacement was performed. Postoperative course was uneventful with the expected remarkable finding of dark urine (Fig. [2](#ccr3710-fig-0002){ref-type="fig"}B).
  
  ![Cervical spondylosis.](CCR3-4-1201-g001){#ccr3710-fig-0001}
  
  ![(A) Calcified "blue" aortic valve signified by arrows (cephalic view). (B) Dark urine.](CCR3-4-1201-g002){#ccr3710-fig-0002}
  
  Alkaptonuric ochronosis is a rare autosomal recessive genetic disorder of tyrosine metabolism and is associated with homogentisic acid oxidase enzyme deficiency due to chromosome 3q mutations resulting in the accumulation of homogentisic acid [1](#ccr3710-bib-0001){ref-type="ref"}. Degenerative arthritis, ochronotic connective tissue pigmentation including structures of the cardiovascular system, and urine darkening are the predominant findings. Aortic valvular stenosis is the most frequent cardiac manifestation [2](#ccr3710-bib-0002){ref-type="ref"}.
  
  Conflict of Interest {#ccr3710-sec-0002}
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  None declared.
  