hyperphenylalaninemia

The presence of abnormally high blood levels of phenylalanine, which may or may not be associated with elevated tyrosine levels, in newborn infants (premature and full-term), associated with the heterozygous state of phenylketonuria, maternal phenylketonuria, or transient deficiency of phenylalanine hydroxylase or p-hydroxyphenylpyruvic acid oxidase.
- malignant h. 1. dHPR-deficient form; an inherited disorder in which there is an absence or deficiency of dihydropteridine reductase (DHPR); this results in impaired regeneration of tetrahydrobiopterin, causing an elevation in phenylalanine levels; 2. gTP-CH form; an inherited disorder in which there is a deficiency of guanosine triphosphate cyclohydrolase, an enzyme used in the biosynthesis of tetrahydrobiopterin; 3. 6-PTS form; an inherited disorder in which there is a deficiency of 6-pyruvoyl tetrahydropterin synthase, an enzyme that participates in the biosynthesis of tetrahydrobiopterin. SYN: nonclassical phenylketonuria.
- non-PKU h. a benign phenotype in which phenylalanine monooxygenase is deficient but is greater than 1% of normal levels.

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hy·per·phe·nyl·al·a·nin·emia or chiefly Brit hy·per·phe·nyl·al·a·nin·ae·mia -.fen-əl-.al-ə-nə-'nē-mē-ə, -.fēn- n the presence of excess phenylalanine in the blood (as in phenylketonuria)
hy·per·phe·nyl·al·a·nin·emic or chiefly Brit hy·per·phe·nyl·al·a·nin·ae·mic -'nē-mik adj

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hy·per·phen·yl·al·a·nin·emia (HPA) (hi″pər-fen″əl-al″ə-nĭ-neґme-ə) 1. any of several autosomal recessive defects in the hydroxylation of phenylalanine resulting in accumulation and excretion of dietary phenylalanine. Most commonly the defect is in the enzyme phenylalanine hydroxylase (PAH); the most severe manifestation of this is phenylketonuria (q.v.), but less severe defects in the enzyme cause non-PKU hyperphenylalaninemia or variant phenylketonuria (qq.v.). Less commonly, the defect is in one of various enzymes involved in synthesis or regeneration of the cofactor tetrahydrobiopterin; see tetrahydrobiopterin deficiency, under deficiency. 2. excess of phenylalanine in the blood.

Medical dictionary. 2011.

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