Question

A 5 year old child was brought to the physician with a history of black urine . There is no history of fever or any other complaints. There is no growth retardation and all the developmental milestones are normal. The child is suspected to have an enzyme defect for metabolism of an aromatic amino acid. What is the enzyme deficient ?

• A. Homogentistae oxidase
• B. Homogentisate dehydrogenase
• C. Tryptophan Hydroxylase
• D. Tyrosine Transaminase

Answer 1

The Correct Option is A

The scenario describes a 5-year-old child presenting with black urine, which is a classic symptom of a condition known as Alkaptonuria. This condition results from a metabolic disorder involving the incomplete breakdown of the amino acid tyrosine, which is an aromatic amino acid.

Alkaptonuria is caused by a deficiency in the enzyme homogentisate oxidase. This enzyme is responsible for breaking down homogentisic acid, a byproduct of tyrosine metabolism. When homogentisate oxidase is deficient, homogentisic acid accumulates in the body, leading to its excretion in urine, which turns black upon oxidation in air.

Given the presented symptoms and the normal growth and developmental milestones, this aligns with the enzymatic defect of homogentisate oxidase deficiency, confirming Alkaptonuria as the condition described in the scenario.