Hyperphenylalaninemia Treatment & Management

Updated: May 18, 2017
  • Author: Eric T Rush, MD, FAAP, FACMG; Chief Editor: Luis O Rohena, MD, MS, FAAP, FACMG  more...
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Treatment

Medical Care

If available, patients should be evaluated at a phenylketonuria (PKU) treatment center. The extent of the hyperphenylalaninemia determines the nature and frequency of follow-up. [4]

In one study, 54% of patients with phenylalanine levels less than 600 µmol/L (10 mg/dL) demonstrated a decline of 30% or more in plasma phenylalanine levels when sapropterin (commercial tetrahydrobiopterin cofactor) was administered at a dose of 10 mg/kg/d. [5] The percentage of patients who responded declined with increasing plasma phenylalanine levels. Response to sapropterin may improve at a dose of 20 mg/kg/d. [6]

Preliminary studies are underway for injectable phenylalanine ammonium lyase, an enzyme substitute. This shows promise in animal studies as an alternative treatment to control phenylalanine levels. [7]

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Consultations

If dietary treatment is necessary, refer the patient to a dietitian experienced with PKU (usually a member of a PKU treatment team).

Refer families of affected infants to a medical geneticist or genetic counselor to review the inheritance of hyperphenylalaninemia.

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Diet

Determine the degree of dietary phenylalanine restriction for each patient based on untreated phenylalanine levels. For more detailed information on a phenylalanine-restricted diet, see Phenylketonuria.

Breastfeeding is usually possible and should not be stopped unless instructed by a local health official or treatment center.

Aspartame should be restricted from diet. Phenylalanine is a primary component of aspartame.

Aspartame may be present in many artificially sweetened substances, including medicines, vitamins, beverages, and foods. A pharmacist can help determine if a medication has a significant amount of aspartame.

The amount of aspartame in a children's vitamin or in a teaspoon of antibiotic may be significant for a child who can tolerate only 200 mg/d of phenylalanine, yet such a dose may be insignificant for a child who can tolerate more than 1000 mg/d.

Stringent phenylalanine-restricted diets have been reported to cause deficiencies of iron, zinc, selenium, and other nutrients and essential amino acids in patients with PKU. The diet requires careful monitoring by a professional trained in PKU management.

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Activity

Do not restrict activities.

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Prevention

In general, patients should avoid consuming aspartame because phenylalanine is a primary component of aspartame.

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Long-Term Monitoring

Phenylalanine levels determine the need for further outpatient care in patients with hyperphenylalaninemia.

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