What is A child has tnicrocephaly, blue eyes, Fair skin, and Mental retardation, Ferric chloride test is positive.What is the likely diagnosis - and explain in detail?
Clinical manifestations of phenylketonuria 

Normal at birth
Symptoms occur after 1 months -


Mental retardation → Not present at birth, develops gradually.
Neurological signs Irritability, tremors, convulsions, hyperkinesis and muscular hypertonia & exaggerated reflex.
Blond hair, blue iris, fair skin.
Musty or mousy body odor.
Vomiting
Microcephaly
Enamel hypoplasia & Growth retardation