#alkaptonuria

• Alkaptonuria — A rare hereditary disorder of aromatic amino acid metabolism (phenylalanine and tyrosine), inherited in an autosomal recessive pattern, caused by a deficiency of the homogentisate 1,2-dioxygenase enzyme. This congenital structural anomaly leads to the accumulation of homogentisic acid (alkapton) in the body, which is excreted in the urine (turning it black upon exposure to air) and deposits in connective tissues and cartilages, causing ochronosis and severe arthropathies in adulthood.