A 6-year-old child presents with black spots on sclera and ear. His urine sample was collected for examination (A). After 30 minutes of collection, the colour of urine sample had changed to (B). What is the most probable enzyme deficiency, child is suffering from?

Alkaptonuria * Autosomal recessive disorder due to deficiency of enzyme homogentisic acid oxidase. Clinical features Ochronosis ( Dark spot on sclera / ear cailage ) Ahritis Darkening of urine on standing ( oxidation of homogentisic Acid) High incidence of Hea disease ( mitral / aoic valvulitis / calcification )