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Title
Phenylketonuria (PKU)
ImagePath
System
Amino acid metabolism disorder
Overview
Autosomal‑recessive deficiency of phenylalanine hydroxylase or BH4 cofactor → inability to convert Phe to Tyr → accumulation of phenyl‑ketones.
Pathophysiology
Accumulated phenylalanine is neurotoxic; deficiency of tyrosine leads to catecholamine and melanin shortage.
Presentation
Normal at birth → by few months: intellectual disability, seizures, eczema, ‘musty/mousy’ body odor, hypopigmented skin, hair & iris.
Diagnosis
Newborn screen: ↑ phenylalanine. Confirm with quantitative plasma amino‑acid analysis.
Management
Life‑long low‑phenylalanine diet (avoid aspartame) + tyrosine supplementation; sapropterin for BH4‑responsive type.
Epidemiology
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