This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
Microcephaly, blue eyes, fair skin, and mental retardation in a 4 year old girl with a positive ferric chloride test is indicative of which of the following? 
Select and explain. 
A. Phenylketonuria (PKU), B. Homocystinuria, C. Tyrosinosis, D. Alkaptonuria
A: Phenylketonuria (PKU)
Answer: A: Phenylketonuria (PKU) 
Explanation: A child presenting with microcephaly blue eyes, fair skin, mental retardation and a positive ferric chloride test typically describes a patient with Phenylketonuria. Ref: Textbook of Biochemistry for Medical Students, By D. M. Vasudevan.M.D, DM Vasudevan, Page 208; Harrison's - 16th Edition, Page 2333