From darkening urine to early diagnosis of alkaptonuria

Abstract

Alkaptonuria is a rare disorder of metabolism characterized by deficiency of homogentisic acid oxidase. Characteristic features include darkening of urine, ochronosis, and arthropathy. Darkening of urine is the only sign of the disorder in the pediatric age group, and it occurs at very early stage of the disorder, as reported by the parents. A 4-year-old boy presented to our clinic with the complaint of dark urine and bluish black staining of clothes. This darkening pointed to a positive physical history of bluish discoloration of sclerae which occurred off and on. We initiated treatment with ascorbic acid and a protein diet with restriction of phenylalanine and tyrosine (1.6 g/kg/d). This case report is significant because of the early diagnosis made.