Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0029713 (immaturity)
 4,335 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phenylketonuria can now be detected during the first few days of life by two reliable mass screening techniques; and its major consequence, severe mental retardation, can be prevented by the early institution of a low phenylalanine diet. Case finding, based on determination of phenylalanine serum levels in newborns before discharge from the hospital, appears to yield an acceptable number of new cases without excessive numbers of false positive or false negative tests at the 4 mg per 100 ml reporting level. Feeding history does not appear to be a major factor in influencing test results. In addition to finding cases of phenylketonuria, newborn blood screening has called attention to another group of infants with hyperphenylalaninemia of other causes. The differential diagnosis in such cases is important because the restrictive diet necessary for patients with phenylketonuria might be harmful to others. Such factors as enzymatic immaturity, heterozygote carriers, maternal enzymatic capacities and other amino-acidemic states must be ruled out by thorough examination. Careful observation, investigation and reporting of experience with these patients will help to eliminate some of the present deficiencies in the knowledge of normal and abnormal amino acid metabolism.
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PMID:Phenylketonuria. Early detection, diagnosis and treatment. 594 92

The cause of hyperphenylalaninemia in sick preterm infants has yet to be determined; one reason may be reduced tolerance to phenylalanine as a consequence of immaturity of phenylalanine hydroxylase. Phenylalanine metabolism was studied in vivo in 23 ventilated preterm infants of gestational age 23 to 36 wk within the first 6 d of life using a continuous i.v. infusion of the stable isotope-labeled amino acids [2H5]phenylalanine, [2H4]tyrosine, and [2H2]tyrosine. Phenylalanine hydroxylation was calculated from two different methods. In the first method, used in all 23 infants receiving glucose and in seven of these infants who subsequently received parenteral nutrition, phenylalanine hydroxylation was calculated from the plasma enrichments of [2H5]phenylalanine and [2H4]tyrosine and from the molar ratio of tyrosine to phenylalanine in mammalian tissue protein. In this instance, the mean hydroxylation was 16.0 (SD 10.9) and 48.4 (SD 14.9) mumol/kg/h, which was 17.3% (SD 8.4%) and 33.2% (SD 9.8% of the total phenylalanine flux for infants receiving glucose and parenteral nutrition, respectively. Additionally, in six infants receiving glucose, hydroxylation was calculated from the measured phenylalanine (2H5), independent tyrosine (2H2) fluxes, and the plasma enrichments of (2H5) phenylalanine and its hydroxylation product [2H4]tyrosine. In this case, hydroxylation was 20.5 (SD 13.0) mumol/kg/h, which represented 22.3% (SD 9.8%) of the phenylalanine flux. In the same six infants, phenylalanine hydroxylation derived using the first method was 22.2 (SD 13.1) mumol/kg/h, 23.6% (SD 9.9%) of the total phenylalanine flux.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Phenylalanine kinetics in sick preterm neonates with respiratory distress syndrome. 789 79

Hyperphenylalaninemia in preterm neonates with heterozygosity for phenylketonuria has previously not been described. We report on a very low birth weight infant, born at a gestational age of 27+5 weeks with a birth weight of 1080 g. Due to a positive family history prenatal diagnosis for phenylketonuria was performed, revealing heterozygosity for classic phenylketonuria. Yet the girl showed hyperphenylalaninemia with a maximum serum phenylalanine concentration of 515 micromol/l on the eighth day of life. Phenylalanine-restrictive parenteral and enteral nutrition was kept from the eighth until the 41st day of life. At term serum phenylalanine concentrations had normalized. We hypothesize that heterozygosity for phenylketonuria may be a risk factor for hyperphenylalaninemia in preterm born infants. Prematurity and the resulting immaturity of liver function with the genetically determined reduced activity of phenylalanine hydroxylase might have caused hyperphenylalaninemia in this girl.
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PMID:Hyperphenylalaninemia in a premature infant with heterozygosity for phenylketonuria. 1534 30