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Phenylketonuria (PKU)
PAH gene
PKU, the most common inborn error of amino acid metabolism in the Caucasian population, is characterized by dietary intolerance to the essential amino acid phenylalanine. Classic PKU is caused by complete or near-complete deficiency of phenylalanine hydroxylase (PAH) activity secondary to mutations in the PAH gene. This autosomal recessive disorder is treatable by dietary restriction of phenylalanine intake as soon as possible after the birth of an infant suspected to have PKU and continuing strict adherence to the diet. Without dietary restriction of phenylalanine, children with classic PKU will develop severe and irreversible mental retardation. Other clinical features evident in untreated children can include microcephaly, epilepsy, behavioral problems, eczema, hypopigmentation, decreased myelin formation and musty urine odor. Infants with PKU may be identified by newborn screening programs upon detection of hyperphenylalaninemia and follow-up biochemical testing. To date, over 520 different mutations have been identified in the PAH gene. Bi-directional sequencing of the entire coding region (exons 1-13) and intron-exon boundaries of the PAH gene will identify more than 95% of mutations.
Testing is performed on genomic DNA obtained from a venous blood sample (2mL for infants, 5mL for adults in EDTA) or from buccal brushes provided by GeneDx (not accepted on infants). Carrier testing of relatives and prenatal diagnosis in at-risk pregnancies are available once the mutations in a family have been defined.
Information Sheet, including prices and CPT codes
Consent Document
Genetic Test Sample Submission Form (Test Requisition Form) including Payment Options
Phenylketonuria, PKU, classic PKU, phenylalanine hydroxylase, inborn error of metabolism, biochemical, amino acid, autosomal recessive, phenylalanine-free, formula, low-protein diet, dietary restriction, mental retardation, microcephaly, epilepsy, newborn screening, hyperphenylalaninemia, mutation, newborn screening
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