Definition (Genet Med 2011;13:697; Pediatrics 2006;118:E934)
• Autosomal recessive d/o: W/ abnormal increase in amino acid phenylalanine in blood
• Deficiency of phenylalanine hydroxylase → impairs neurotransmitter production
• If >20 mg/dL accumulation of phenyl ketones → phenylketonuria (PKU) & musty body odor
• Spectrum of severity depending on degree of residual enzyme function; in most if untreated → severe brain damage, MR, seizures, spasticity
Incidence
• ∼1:15,000 for PKU (most common in Turkish (1/2,600) and Irish populations (1/4,500))
Treatment
• Early Rx important → admit to the hospital, inverse relationship btw time to Rx and IQ
• Positive NBS → check quantitative level of phenylalanine and tyrosine concentration
• Provide w/ protein sources low in phenylalanine; titrate to [Phe] 1–6 mg/dL for 1st 10 yr of life
• Follow phenylalanine levels; despite Rx pts w/ ↑ neuropsych complications