Alkaptonuria, also called endogenous ochronosis, and also called as Black Urine Disease, is a rare metabolic autosomal recessive disorder. It occurs by complete inhibition of homogentisic acid oxidase enzyme having its deposition in various tissues. Alkaptonuria is caused due to deficiency of homogentisic acid oxidase involved in the metabolism of tyrosine. Dark discolouration of urine, ochronosis at cartilage and connective tissues, arthritis at the third of fourth decade of life, renal stone disease, spontaneous tendon rupture etc. May be seen in alkaptonuria. Disease severity varies among individual patients, even between siblings, and increase with age because of homogentisic acid accumulation. Usually, life span is not shortened in AKU, but the quality of life is severely effected. Several studies have suggested that Nitisinone may be effective in the treatment of alkaptonuria. Characteristically, the excess HGA means sufferers pass dark urine, which upon standing turns black. This is a feature present from birth. Over time patients develop other manifestations of AKU, due to the deposition of HGA in collagenous tissues, namely ochronosis and ochronotic osteoarthropathy. Although this condition does not reduce life expectancy, it significantly affects the quality of life. The natural history of this condition is becoming better understood, despite gaps in knowledge. Clinical assessment of the condition has also improved along with the development of potentially disease-modifying therapy. Furthermore, recent developments in AKU research have to lead to new understanding of the disease, and further study of the AKU arthropathy has the potential to influence therapy in the management of osteoarthritis
