A normal bom child presents with mental retardation, blond hair and convulsions at 1 year of age. Most probable diagnosis is?

ANSWER: (B) PhenylketonuriaREF: Nelson 18th ed chapter 85.1, Harrison's 17th Ed Ch 358See table of "DISORDERS OF PHENYL ALANINE METABOLISM" in Biochemistry 2013 Session 2CLASSIC PHENYLKETONURIA (PKU) CLINICAL MANIFESTATIONS:The affected infant is normal at birth.Mental retardation may develop gradually and may not be evident for the 1st few months.Vomiting, sometimes severe enough to be misdiagnosed as pyloric stenosis, may be an early symptom.Older untreated children become hyperactive, with purposeless movements, rhythmic rocking, and athetosis.Infants are lighter in their complexion than unaffected siblings with blonde hairsThese children have an unpleasant odor of phenylacetic acid, which has been described as musty or mousey.Most infants are hypertonic with hyperactive deep tendon reflexes.About 25% of children have seizures, and more than 50% have electroencephalographic abnormalities.Microcephaly, prominent maxilla with widely spaced teeth, enamel hypoplasia, and growth retardation are other common findings in untreated children.