This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetic and genetic disorders, Subject name: Pediatrics
One year old male child with sparse blond hair, developmental delay and tremors, diagnosis 
Select and explain. 
A. Albinism, B. Phenylketonuria, C. Cerebral palsy, D. Infantile tremor syndrome
B: Phenylketonuria
Answer: B: Phenylketonuria 
Explanation: Phenylketonuria is due to deficiency of enzyme phenylalanine hydroxylase or of its cofactor tetrahydrobiopterin ;leads to accumulation of phenylalanine in body fluids and brain. It is mainly characterized by profound mental retardation ,lighter complexion and neurologic symptoms like tremors,hyperreflexia and spasticity. Reference: Nelson TB of pediatrics 19th edition, pg 418