Alkaptonuric ochronosis of the carotid artery

Alkaptonuria is a rare autosomal-recessive metabolic disorder of tyrosine degradation which results in elevated levels of circulating homogentisic acid. Ochronosis occurs when homogentisic acid polymerizes and deposits in connective tissue. Ochronotic lesions in the carotid arteries have not been described. In this report, we describe a 65-year-old man with alkaptonuria, with hypertension and hyperlipidemia, who underwent an uneventful carotid endarterectomy for an asymptomatic high-grade internal carotid artery stenosis. Histology revealed homogentisic acid deposits as black-brownish areas in the intima. He was noted to have an impressive heavily brown-black pigmented discoloration of the carotid plaque. Cardiovascular involvement is a rare consequence of alkaptonuria and is manifested by pigment deposition at the areas influenced by shear stress and turbulence.