Alcaptonurie, ochronose et arthropathie ochronotique

Abstract: Authors describe biological, tissular and clinical aspects of the three disease''s stages: alkaptonuria, ochronosis and ochronotic arthropathy. For ochronotic arthropathy, which appears around the fourth decade of life, they portray clinical and radiological findings valuable to establish diagnosis by the rheumatologist. They list clinical and paraclinical examinations to perform. Evolution, complications mainly of renal and cardiac systems and treatment options are also reviewed. Alkaptonuria (AKU) or “black urine disease”, is a rare autosomal recessive inborn error of metabolism concerning the hepatic catabolism of aromatic aminoacid, l-phenylalanine and l-tyrosine. AKU results in lack of activity of the enzyme, homogentisate 1,2-dioxygenase (HGD) in the liver, which leads to storage of homogentisic acid (HGA), a colorless diphenolic acid. Hepatic HGA diffuses into blood, flood all connective tissues of organism, then is excreted by urines. In urines, HGA oxidizes to form benzoquinone acetate (BQA), and then form brown-black melanin-like pigments polymers, hence the name of alcaptone. This is the first stage of the disease, evidenced since birth. The same steps occur in tissues but more slowly than in urines, with deposition of pigments in connective tissues leading to visible ochronosis, mainly in ear and sclera. This is the second disease''s stage occurring during the third decade of life. [Copyright &y& Elsevier]