title: Adjusting diet with sapropterin in phenylketonuria: what factors should be considered?
abstract: The usual treatment for phenylketonuria (PKU) is a phenylalanine-restricted diet. Following this diet is challenging, and long-term adherence (and hence metabolic control) is commonly poor. Patients with PKU (usually, but not exclusively, with a relatively mild form of the disorder) who are responsive to treatment with pharmacological doses of tetrahydrobiopterin (BH4) have either lower concentrations of blood phenylalanine or improved dietary phenylalanine tolerance. The availability of a registered formulation of BH4 (sapropterin dihydrochloride, Kuvan®) has raised many practical issues and new questions in the dietary management of these patients. Initially, patients and carers must understand clearly the likely benefits (and limitations) of sapropterin therapy. A minority of patients who respond to sapropterin are able to discontinue the phenylalanine-restricted diet completely, while others are able to relax the diet to some extent. Care is required when altering the phenylalanine-restricted diet, as this may have unintended nutritional consequences and must be undertaken with caution. New clinical protocols are required for managing any dietary change while maintaining control of blood phenylalanine, ensuring adequate nutrition and preventing nutritional deficiencies, overweight or obesity. An accurate initial evaluation of pre-sapropterin phenylalanine tolerance is essential, and the desired outcome from treatment with sapropterin (e.g. reduction in blood phenylalanine or relaxation in diet) must also be understood by the patient and carers from the outset. Continuing education and support will be required thereafter, with further adjustment of diet and sapropterin dosage as a young patient grows.
authors.affiliation: The Children’s Hospital, Birmingham, West Midlands, UK. anita.macdonald@bch.nhs.uk
authors.forename: Anita
authors.initials: A
authors.lastname: MacDonald
authors.forename: Kirsten
authors.initials: K
authors.lastname: Ahring
authors.forename: Katharina
authors.initials: K
authors.lastname: Dokoupil
authors.forename: Hulya
authors.initials: H
authors.lastname: Gokmen-Ozel
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Lammardo
authors.forename: Kristina
authors.initials: K
authors.lastname: Motzfeldt
authors.forename: Martine
authors.initials: M
authors.lastname: Robert
authors.forename: Júlio César
authors.initials: JC
authors.lastname: Rocha
authors.forename: Margreet
authors.initials: M
authors.lastname: van Rijn
authors.forename: Amaya
authors.initials: A
authors.lastname: Bélanger-Quintana
mesh_terms: D001708:Biopterins / Q000031:analogs & derivatives* / Q000627:therapeutic use; D002985:Clinical Protocols; D005247:Feeding Behavior; D006801:Humans; D010649:Phenylalanine / Q000008:administration & dosage* / Q000097:blood; D010661:Phenylketonurias / Q000178:diet therapy* / Q000188:drug therapy*
chemical_list: D001708:Biopterins; D010649:Phenylalanine; C003402:sapropterin