Genetic Disorders · NEET PG Preparation Paediatrics
A 2-day-old term newborn is evaluated for lethargy, poor feeding, and tachypnea. Laboratory investigations reveal a severe high anion gap metabolic a…
Practice question from Genetic Disorders (NEET PG Preparation Paediatrics), with the correct answer and a step-by-step solution.
hard · MCQ · Q-588DD3
A 2-day-old term newborn is evaluated for lethargy, poor feeding, and tachypnea. Laboratory investigations reveal a severe high anion gap metabolic acidosis, hyperammonemia with normal plasma citrulline levels, and ketosis. Urine analysis shows massive excretion of methylcitric acid and propionylcarnitine. Which of the following is the most likely enzyme deficiency?
- A.Phenylalanine hydroxylase
- B.Propionyl-CoA carboxylaseCorrect answer
- C.Ornithine transcarbamylase
- D.Glucose-6-phosphatase
Solution
Propionic acidemia is an autosomal recessive organic acidemia caused by a deficiency of propionyl-CoA carboxylase. It classically presents in the neonatal period with lethargy, vomiting, ketoacidosis, hyperammonemia, and bone marrow suppression. The accumulation of propionyl-CoA derivatives leads to elevated methylcitric acid in the urine and elevated propionylcarnitine on newborn screening. Ornithine transcarbamylase deficiency causes hyperammonemia without metabolic acidosis.
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