Late-diagnosed phenylketonuria in an eight-year-old boy with dyslexia and attention-deficit hyperactivity disorder

Area of Science:

• Biochemistry
• Neuroscience
• Genetics

Background:

• Phenylketonuria (PKU) is a metabolic disorder historically linked to severe intellectual disability.
• Newborn screening programs have made early diagnosis and treatment of classical PKU highly effective.
• Untreated PKU can lead to irreversible brain damage and significant neurodevelopmental deficits.

Observation:

• A male patient presented with dyslexia and attention-deficit hyperactivity disorder (ADHD) at eight years of age.
• The patient was diagnosed with a mild form of phenylketonuria.
• This diagnosis occurred significantly later than typical newborn screening.

Findings:

• Late diagnosis of mild phenylketonuria can still impact neurobehavioral outcomes.
• Cognitive and behavioral symptoms may indicate underlying metabolic disorders like PKU.
• Phenylalanine hydroxylase deficiency, even in milder forms, requires consideration in differential diagnoses.

Implications:

• Earlier recognition and intervention for phenylketonuria are crucial for optimal neurobehavioral development.
• Expanding differential diagnoses to include milder metabolic disorders is essential for complex neurodevelopmental cases.
• This case underscores the importance of continued vigilance for PKU beyond standard newborn screening protocols.