A 5 year old child presents with mental retardation, seizures, with lighter skin complexion. The diagnosis is

(C) Phenylketonuria# Phenylketonuria: Phenylketonuria (PKU) is a disorder that causes a buildup of the amino acid phenylalanine, which is an essential amino acid that cannot be synthesized in the body but is present in food.> Most affected newborns are detected during routine screening tests. Newborns with PKU rarely have symptoms right away, although sometimes an infant is sleepy or eats poorly.> If not treated, affected infants progressively develop mental retardation over the first few years of life, which eventually becomes severe.> Other symptoms include seizures, nausea and vomiting, an eczema-like rash, lighter skin and hair than their family members, aggressive or self-injurious behavior, hyperactivity, and sometimes psychiatric symptoms.> Untreated children often give off a "mousy" body and urine odor as a result of a by-product of phenylalanine (phenylacetic acid) in their urine and sweat.