Three-year audit of the hyperphenylalaninaemia/phenylketonuria spectrum in Victoria.
OBJECTIVE
To determine the prevalence, the types and severity of hyperphenylalaninaemia (including phenylketonuria (PKU)) in Victoria and to report on a new treatment modality of PKU.


METHODS
We reviewed the medical records of all patients diagnosed with high blood phenylalanine levels by newborn screening between November 2001 and October 2004.


RESULTS
We identified 17 newborn babies with high levels of blood phenylalanine (total samples: 190,835). Dihydrobiopterin reductase deficiency was excluded in all babies. Five babies had persistent phenylalanine levels of 200-300, and do not receive any dietary or pharmaceutical therapy. One baby was diagnosed as having pyruvoyl tetrahydro-pterin synthase deficiency. Following reports of tetrahydrobiopterin (BH(4))-responsive PKU, we have performed a BH(4) load (20 mg/kg, 6R-5,6,7,8-tetrahydro-L-biopetrin dehydrochloride; Schricks Laboratories, Jona, Switzerland) in 10 newborn babies with PKU (one baby with a phenylalanine level of 2600 micromol/L was started on diet without prior load). Three babies had a significant response to BH(4) (>35% decrease in phenylalanine level). Protein restriction (1.2 g/kg/day) and introduction of phenylalanine-free formula, in addition to BH(4) treatment, were necessary in one patient. The other patients maintain good metabolic control with BH(4) treatment only (at approximately 11 mg/kg/day) and an intake of 2-3 g protein per day. Of the nine babies who are on a full PKU diet, three have high phenylalanine tolerance (consistently >40 mg/kg/day).


CONCLUSIONS
There is a spectrum of severity of hyperphenylalaninaemia in the population. The detection of BH(4)-responsive PKU patients offers them a less restrictive dietary regimen and an improved quality of life, and may enable near normal life-style in adolescence.
Boneh
Avihu
A
Metabolic Service, Genetic Health Services Victoria, Royal Children's Hospital, Parkville, Vic., Australia. avihu.boneh@ghsv.org.au
Francis
Dorothy E M
DE
Humphrey
Maureen
M
Upton
Helen J
HJ
Peters
Heidi L
HL
D001708:Biopterins / Q000031:analogs & derivatives* / Q000627:therapeutic use; D003131:Combined Modality Therapy; D018753:Diet, Protein-Restricted; D006801:Humans; D041943:Infant Formula; D007231:Infant, Newborn; D015997:Neonatal Screening; D010649:Phenylalanine / Q000097:blood* / Q000187:drug effects; D010661:Phenylketonurias / Q000145:classification / Q000453:epidemiology* / Q000628:therapy; D015995:Prevalence; D012189:Retrospective Studies; D014739:Victoria / Q000453:epidemiology
D001708:Biopterins; D010649:Phenylalanine; C003402:sapropterin