Alkaptonuria and ochronosis. A survey and 5 cases

A survey of alkaptonuria and ochronosis is given, based on the literature and on 5 additional cases. The disease, which is autosomal recessive, results from a decreased amount of the enzyme homogentisic acid oxidase, due to which tyrosine and phenylalanine cannot be broken down via the normal pathway. The diagnosis is made by determination of urinary urinary homogentisic acid excretion, as the clinical and radiological findings are not pathognomonic. The symptoms, which extend over decades, result from the deposition of pigment in the extracellular macromolecules of the connective tissue, particularly of the skin and joints.