Phenylketonuria (PKU)


Phenylketonuria (PKU) is an autosomal recessive disorder caused by defects in metabolizing phenylalanine to tyrosine (See Catecholamine Synthesis).

Excess phenylalanine is converted into phenylketones in the urine, giving rise to the name, phenylketonuria. PKU can be caused by defects in phenylalanine hydroxylase or its BH4 cofactor. Since tyrosine cannot be produced from phenylalanine, tyrosine becomes essential in the diet.

Clinical features include seizures and cognitive delays. Growth retardation and failure to thrive is observed, and on exam, patients will often have a light or fair complexion, eczema, and a characteristic musty body odor. Diagnosis is delayed 2-3 days after birth since infants are normal at birth due to the presence of maternal enzymes.

Find this Phenylketonuria mnemonic and more mnemonics for Metabolic Disorders among Pixorize's visual mnemonics for the USMLE Step 1 and NBME Shelf Exams.