Question

An infant presents with vomiting after feeding. A Benedict’s test was performed and returned positive for a non-glucose substance. Which of the following is the most likely diagnosis?

• A. Galactosemia due to GAL-1-P uridyl transferase enzyme deficiency
• B. Hereditary fructose intolerance due to aldolase B deficiency
• C. Glucose-6-Phosphate dehydrogenase (G6PD) deficiency
• D. Galactosemia due to galactokinase enzyme deficiency

Hint:

In infants with vomiting after feeding and a positive Benedict's test, consider galactosemia. The absence of GAL-1-P uridyl transferase enzyme activity is the most common cause.

Answer 1

The Correct Option is A

Step 1: Interpret the Benedict's test clue first.
Benedict's reagent turns positive with REDUCING sugars. The stem tells us the positive result is due to a NON-glucose reducing substance, so glucose itself is not the culprit. In a milk-fed infant, the reducing sugar that floods the system is galactose (from lactose). This already tilts us toward a disorder of galactose metabolism.

Step 2: Tie the timing of symptoms to the feed.
The baby vomits AFTER FEEDING on milk. A condition that becomes symptomatic the moment milk (lactose → galactose) is introduced must sit on the galactose pathway and must be severe enough to cause toxicity early. That severity points to classic galactosemia.

Step 3: Localise the enzyme block.
Classic galactosemia is caused by deficiency of galactose-1-phosphate uridyltransferase (GALT). The block lets toxic galactose-1-phosphate accumulate (damaging liver, kidney, brain → vomiting, jaundice, hepatomegaly), while free galactose spills into blood and urine, giving the positive non-glucose Benedict's reaction.

Step 4: Rule out the alternatives.
• Hereditary fructose intolerance (aldolase B) → triggered by FRUCTOSE/sucrose, so symptoms appear after weaning onto fruits/sweets, not with early milk feeds.
• G6PD deficiency → causes oxidative haemolysis after triggers, not post-feed vomiting, and does not give a non-glucose reducing sugar.
• Galactokinase deficiency → also a galactosemia and Benedict-positive, but it is the milder variant whose dominant problem is cataracts, lacking the severe acute vomiting/hepatic picture seen here.

Final answer: The severe milk-triggered presentation with a non-glucose reducing sugar is Galactosemia due to GAL-1-P uridyl transferase enzyme deficiency (Option 1).