Hyperphenylalaninemia Workup

  • Author: Georgianne L Arnold, MD; Chief Editor: Bruce Buehler, MD   more...
 
Updated: Mar 1, 2012
 

Laboratory Studies

Screening for hyperphenylalaninemia includes the following:

  • Newborns with abnormal screening findings should be monitored in accordance with local regulations. Different states or authorities may have various protocols regarding result interpretation and follow-up. Do not restrict dietary phenylalanine or interrupt breastfeeding based on screening results unless instructed by a health official or treatment center. However, immediately refer the patient to a treatment center for confirmatory testing.
  • Low-grade elevations may require repeat screening. Phenylalanine levels can rise for several weeks after birth in children with hyperphenylalaninemia or phenylketonuria (PKU). A low-grade elevation 24-72 hours following birth might signal true PKU, not merely hyperphenylalaninemia.

Measure plasma phenylalanine and tyrosine levels as soon as possible after an abnormal screening result. An elevated phenylalanine level with low or normal tyrosine level is expected. Remember that patients with liver disease or tyrosinemia typically have elevated phenylalanine and tyrosine levels.

Obtain blood and urine biopterins assays through a qualified laboratory to exclude a tetrahydrobiopterin defect.

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Procedures

Diagnostic procedures, such as phenylalanine or biopterin loading tests, are rarely indicated.

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Contributor Information and Disclosures
Author

Georgianne L Arnold, MD  Faculty, Department of Pediatrics, Divison of Genetics, University of Pittsburgh School of Medicine

Georgianne L Arnold, MD is a member of the following medical societies: American College of Medical Genetics, American Society of Human Genetics, Society for Inherited Metabolic Disorders, and Society for the Study of Inborn Errors of Metabolism

Disclosure: Biomarin Grant/research funds clinical trial

Specialty Editor Board

Christian J Renner, MD  Consulting Staff, Department of Pediatrics, University Hospital for Children and Adolescents, Erlangen, Germany

Disclosure: Nothing to disclose.

Mary L Windle, PharmD  Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

Margaret M McGovern, MD, PhD  Professor and Chair of Pediatrics, Stony Brook University, New York

Margaret M McGovern, MD, PhD is a member of the following medical societies: American Academy of Pediatrics and American Society of Human Genetics

Disclosure: Genzyme Grant/research funds PI

Paul D Petry, DO, FACOP, FAAP  Consulting Staff, Freeman Pediatric Care, Freeman Health System

Paul D Petry, DO, FACOP, FAAP is a member of the following medical societies: American Academy of Osteopathy, American Academy of Pediatrics, American College of Osteopathic Pediatricians, and American Osteopathic Association

Disclosure: Nothing to disclose.

Chief Editor

Bruce Buehler, MD  Professor, Department of Pediatrics and Genetics, Director RSA, University of Nebraska Medical Center

Bruce Buehler, MD is a member of the following medical societies: American Academy for Cerebral Palsy and Developmental Medicine, American Academy of Pediatrics, American Association on Mental Retardation, American College of Medical Genetics, American College of Physician Executives, American Medical Association, and Nebraska Medical Association

Disclosure: Nothing to disclose.

References

  1. Prick BW, Hop WC, Duvekot JJ. Maternal phenylketonuria and hyperphenylalaninemia in pregnancy: pregnancy complications and neonatal sequelae in untreated and treated pregnancies. Am J Clin Nutr. Feb 2012;95(2):374-82. [Medline].

  2. Mak CM, Ko CH, Lam CW, Lau WL, Siu WK, Chen SP, et al. Phenylketonuria in Hong Kong Chinese: a call for hyperphenylalaninemia newborn screening in the Special Administrative Region, China. Chin Med J (Engl). Aug 2011;124(16):2556-8. [Medline].

  3. Ten Hoedt AE, Hollak CE, Boelen CC, van der Herberg-van de Wetering NA, Ter Horst NM, Jonkers CF, et al. "MY PKU": increasing self-management in patients with phenylketonuria. A randomized controlled trial. Orphanet J Rare Dis. Jun 27 2011;6:48. [Medline]. [Full Text].

  4. Burton BK, Grange DK, Milanowski A, et al. The response of patients with phenylketonuria and elevated serum phenylalanine to treatment with oral sapropterin dihydrochloride (6R-tetrahydrobiopterin): a phase II, multicentre, open-label, screening study. J Inherit Metab Dis. Oct 2007;30(5):700-7. [Medline].

  5. Matalon R, Michals-Matalon K, Koch R, et al. Response of patients with phenylketonuria in the US to tetrahydrobiopterin. Mol Genet Metab. Dec 2005;86 Suppl 1:S17-21. [Medline].

  6. Sarkissian CN, Gamez A, Wang L, et al. Preclinical evaluation of multiple species of PEGylated recombinant phenylalanine ammonia lyase for the treatment of phenylketonuria. Proc Natl Acad Sci U S A. Dec 30 2008;105(52):20894-9. [Medline].

  7. Agostoni C, Verduci E, Massetto N, et al. Long term effects of long chain polyunsaturated fats in hyperphenylalaninemic children. Arch Dis Child. Jul 2003;88(7):582-3. [Medline].

  8. Berlin CM, Levy HL, Hanley WB. Delayed increase in blood phenylalanine concentration in phenylketonuric children initially classified as mild hyperphenylalaninemia. Screening. 1995;4:35-39.

  9. Diamond A, Prevor MB, Callender G. Prefrontal cortex cognitive deficits in children treated early and continuously for PKU. Monogr Soc Res Child Dev. 62(4):i-v, 1-208. [Medline].

  10. Fisch RO, Matalon R, Weisberg S, Michals K. Phenylketonuria: current dietary treatment practices in the United States and Canada. J Am Coll Nutr. Apr 1997;16(2):147-51. [Medline].

  11. Gassio R, Artuch R, Vilaseca MA, et al. Cognitive functions in classic phenylketonuria and mild hyperphenylalaninemia: experience in a pediatric population. Dev Med Child Neurol. 2005;47:443-8. [Medline].

  12. Medical Research Council Working Party on Phenylketonuria. Recommendations on the dietary management of phenylketonuria. Arch Dis Child. Mar 1993;68(3):426-7. [Medline].

  13. Scriver CR, Kaufman S, Eijsensmith RC. The hyperphenylalaninemias. In: The Metabolic and Molecular Bases of Inherited Disease. Vol 1. 1995:1015-76.

 
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Phenylalanine hydroxylase converts phenylalanine to tyrosine.
 
 
 
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