Intellectual performance of 36 phenylketonuria patients and their nonaffected siblings

Area of Science:

• Medical Genetics
• Neurodevelopmental Disorders
• Metabolic Disorders

Background:

• Phenylketonuria (PKU) is a rare genetic disorder requiring early dietary management.
• Untreated PKU leads to severe intellectual disability.
• The impact of early, rigorous treatment on cognitive outcomes is still under investigation.

Purpose of the Study:

• To assess the long-term cognitive function in children with PKU treated from infancy.
• To compare the intellectual performance of PKU patients with their unaffected siblings.

Main Methods:

• A cohort of 36 children diagnosed with PKU and treated before 121 days of age was studied.
• Participants and their age-matched, unaffected siblings were administered the Stanford-Binet Intelligence Scale.
• Cognitive scores were compared between the PKU group and the control sibling group.

Main Results:

• PKU patients (mean IQ 94) showed a statistically significant, albeit small, difference compared to their siblings (mean IQ 99).
• The five-point mean IQ difference was significant at the .02 level.
• This suggests a subtle intellectual impairment may persist despite early and consistent dietary therapy.

Conclusions:

• Early and rigorous dietary treatment for PKU may not fully normalize intellectual function.
• A minimal intellectual deficit might be associated with PKU even with optimal management.
• Further research is warranted to understand the nuances of cognitive development in treated PKU patients.