- Branched-chain alpha-keto acid dehydrogenase complex is missing or defective
- Oxidative decarboxylation of alpha-ketoacids from branched-chain AA, (Ile Val Leu) does not occur
- Build up of these alpha-ketoacids and branched-chain AA in blood and urine
- Severe mental deficiency
- Failure to thrive
- Screening in NB blood sample
- Restricted diet


Michigan State University

- Phenylketonuria (PKU)
- Alkaptonuria
- Maple-Syrup urine disease

Inborn Errors of Amino Acid Catabolism

Phenylketonuria (PKU) is an inherited metabolic disorder caused by a recessive gene, meaning a child must inherit a copy of the mutated allele from each parent to develop the condition. Individuals with PKU lack the enzyme needed to metabolize the amino acid phenylalanine. If the condition is not treated through a regulated diet, the resulting buildup of phenylalanine in the brain becomes toxic, leading to severe consequences such as significant deficits in cognitive function, intellectual disability, seizures, and an increased risk of various psychiatric disorders.

Phenylketonuria (PKU)

- Absence of enzyme homogentisate oxigenase
- Excreted in urine and produces melanin-like dark pigment when oxidized by air - black urine
- Relatively benign disease as homogentisate can be excreted


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