Marked reduction of homogentisic acid with nitisinone in a child with alkaptonuria: a case report

Alkaptonuria (AKU) is a rare autosomal recessive disorder caused by mutations in the homogentisate 1,2-dioxygenase (HGD) gene, resulting in impaired degradation of tyrosine and phenylalanine and subsequent accumulation of homogentisic acid (HGA). While dark urine may be the only clinical sign in childhood, progressive HGA deposition leads to severe manifestations in adulthood, including arthritis and cardiovascular complications. We report the case of a 10-year-old boy in whom alkaptonuria was diagnosed early and successfully managed with Nitisinone, an inhibitor of 4-hydroxyphenylpyruvate dioxygenase that reduces HGA production. Nitisinone represents a cornerstone of AKU management, though vigilant monitoring for hypertyrosinemia remains essential, especially in children.