Alkaptonuria

Alkaptonuria also known as alcaptonuria or ochronosis is a rare inherited, genetic disorder of tyrosine metabolism. This is an autosomal recessive trait that is caused by defect in the enzyme homogentisic acid oxidase.

The characteristic of alkaptonuria is that urine exposed to air turn dark (or black) after several hours. In adulthood persons suffering from alkaptonuria develop progressive arthritis (especially of the spine). This is caused by accumulation of a by-product, homogentisic acid, that is excreted in urine and damages bones and cartilages.

Prevention is not possible and the treatment is aimed at ameliorating symptoms.