A 6-year-old child is brought to the OPD with a history of mental retardation, failure to walk , failure to grow, seizures, hyperactivity, and tremors. On examination, there is microcephaly, fair hair, light skin color, and blue eyes. Which of the following enzyme is deficient in this child?: (A) Homogentisate dioxygenase, (B) Tyrosinase, (C) Fumaryl acetoacetate hydroxylase, (D) Phenylalanine hydroxylase
Answer is D. The given clinical manifestations point to the diagnosis of Phenylketonuria (PKU). Deficiency of the enzyme phenylalanine hydroxylase Reference: Harpers illustrated biochemistry 30th edition