Alkaptonuria: Clinical Spectrum of a Diagnosed Case in Bahrain With a Literature Review

Alkaptonuria (AKU) is a rare metabolic condition caused by mutations within a gene coding for homogentisate 1,2 dioxygenase enzyme involved in the tyrosine catabolism pathway. This mutation will result in the accumulation of homogentisic acid (HGA) in the body. AKU is a multi-systemic slowly progressing disease. The onset of its clinical presentation may vary based on the extensive disposition of the HGA. Initially, it might be asymptomatic, and symptoms usually appear in the second or third decades due to the formation of HGA, melanin compounds that accumulate in the cartilage leading to ochronosis. Furthermore, by the fourth or fifth decade, ochronotic arthropathy occurs, along with other extra-articular complications such as cardiovascular manifestations (e.g., valvular heart disease), renal and prostatic stones, and hypothyroidism. Management of this condition is mainly symptomatic, focusing on the treatment of its complications. Recently, the use of nitisinone (NTBC) has shown stabilization of disease manifestations. In this report, we present in detail the first AKU-diagnosed patient, including the clinical presentations, radiological findings, genetic results, and clinical outcomes, from the main tertiary hospital in Bahrain. Moreover, we conducted a thorough literature review on this rare condition.