Course : MOC Part IV: Phenylketonuria Due to Phenylalanine Hydroxylase Deficiency

Phenylketonuria (PKU) is a disorder of amino acid metabolism in which the amino acid phenylalanine (phe) from protein cannot be metabolized to tyrosine.  Greater than 95% of cases are due to deficient activity of the liver enzyme, phenylalanine hydroxylase (PAH) resulting in an elevation in blood phe levels, which has a toxic effect on the developing central nervous system, and if untreated leads to intellectual disability.   In a minority of individuals (<5%) with elevated phe levels, the PAH enzyme dysfunction results from abnormal synthesis or recycling of the biopterin cofactor, leading to neurotransmitter deficiencies as well as the other symptoms of PKU.  All affected patients require quality medical services from a metabolic specialist, including diagnostic confirmation, clinical evaluation, laboratory testing, diet and disease management and genetic counseling.  


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