Diverse Expression of Alkaptonuria: A Case Series

Alkaptonuria is a rare autosomal metabolic disorder that predominately affects the male population. In infants, it is usually asymptomatic except darkening of urine on exposure, while in adults it starts appearing in 3rd and 4th decade of life. We received 4 cases of this rare disease at the Department of Toxicology, Armed Forces Institute of Pathology Rawalpindi, Pakistan, from Jan 2020 to Feb 2023 presenting in different age groups ranging from early childhood to middle age with a common clinical finding of darkening of urine on prolonged standing. Urine samples of cases were analyzed by gas chromatography-mass spectrometry (GC-MS) and matched with the reference library of GC-MS for the peak of homogentisic acid (HGA) on urine organic acid (UOA).