Alkaptonuria: a Presentation of Two Turkish Cases

Alkaptonuria is a rare, inherited metabolic disorder caused by a deficiency in homogentisic acid (HGA) oxygenase oxidase. HGA, an intermediary product in the metabolism of phenylalanine and tyrosine, cannot be further metabolised in cases of alkaptonuria. The metabolic defect causes a characteristic triad of homogentisic aciduria, ochronosis and arthritis. HGA is excreted in urine, turning dark brown or black upon oxygenation and alkalinisation. With complaints of black-colored urine without any other findings and increased urinary HGA excretion confirmed by gas chromatography-mass spectrometry, two cases, three-and ten-year-old boys, are presented and the relevant literature is discussed.