Alkaptonuria: clinical manifestations and an updated approach to treatment of a rare disease.

Alkaptonuria (AKU) is a rare autosomal recessive disorder with a global incidence of 1 in 250 000 to 1 million people worldwide. It results from a deficiency of the enzyme homogentisic acid (HGA) oxidase which when absent, leads to an accumulation of HGA. Without this enzymatic degradation, HGA deposits in connective tissues resulting in pigmentation (ochronosis), plaque formation and accelerated cartilage destruction. With this, many patients who suffer from AKU develop ochronotic arthropathies, tendon ruptures, fractures, and chronic joint pain. Similarly, patients can develop cardiac valvular dysfunction and interstitial renal disease. Our two cases highlight the array of pathologies seen in AKU and, in light of newly published research, give us a platform from which we can discuss the developments in management of this rare disease.