A Rare Diagnosis in a Resource-Limited Setting: Alkaptonuria in a Young Dominican Child

Alkaptonuria (AKU) is a rare metabolic genetic disorder transmitted in an autosomal recessive pattern caused by a deficiency in the activity of the enzyme homogentisate 1,2-dioxygenase (HGD), leading to progressive accumulation of oxidized homogentisic acid (HGA) as a dark pigment in connective tissues, cartilage, and organs in a process called ochronosis. Polymerization of HGA causes urine darkening after a few hours of exposure to the atmosphere, which is a hallmark of AKU. We present the case of a 3-year-old boy from a rural community in the Dominican Republic assessed at the pediatric hospital due to dark urine. The patient was directed to urology for suspicion of hematuria and later referred to the genetic pediatrics department in the absence of bleeding or urologic structural abnormalities. Afterward, a qualitative urine test and subsequent molecular testing via exome sequencing identified two heterozygous pathogenic variants in the HGD gene. Management consisted of a protein-restricted diet and vitamin C supplementation as an antioxidant. This case report emphasizes the importance of early detection and referral to a pediatric geneticist for prompt management, utilizing a multidisciplinary approach, to prevent complications and address the challenges associated with diagnosis and treatment in resource-limited settings and low-income families.