This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Disorders of Amino acid Metabolism, Subject name: Pediatrics
HHH syndrome is caused by defect in: 
Select and explain. 
A. Ornithine permease, B. Ornithine transcarbamyolase, C. Arginase, D. Argininosuccinase lyase
A: Ornithine permease
Answer: A: Ornithine permease 
Explanation: Hyperammonemia-Hyperornithinemia-Homocitrullinemia (HHH) Syndrome: autosomal recessive disorder Defect is in transpo system of ornithine from cytosol into mitochondria Accumulation of ornithine in the cytosol and a deficiency of ornithine inside mitochondria.