Only few cases of classical phenylketonuria (PKU) in premature infants
have been reported. Treatment of these patients is challenging due to the
lack of a phenylalanine-free amino acid solution for parenteral infusion.
The boy was born at 27 weeks of gestation with a weight of 1000 g (P10).
He received parenteral nutrition with a protein intake of 3 g/kg/day. On day
7 he was diagnosed with classical PKU (genotype IVS10-11G>A/IVS12+
1G>A) due to highly elevated phenylalanine (Phe) level in newborn
screening (2800 micromol/L). His maximum plasma Phe level reached
3696 micromol/L. Phe intake was stopped for 4 days. During this time the
boy received intravenous glucose and lipids as well as little amounts of
Phe-free formula by a nasogastric tube. Due to a deficit of essential amino
acids and insufficient growth, a parenteral nutrition rich in branched-chain
amino-acids and relatively poor in Phe was added, in order to promote
protein synthesis without overloading in Phe. Under this regimen, Phe
plasma levels normalized on day 19 when intake of natural protein was
started. The boy has now a corrected age of 2 years. He shows normal
growth parameters and psychomotor development.
Despite a long period of highly elevated Phe levels in the postnatal
period our patient shows good psychomotor development. The
management of premature infants with PKU depends on the child's
tolerance to enteral nutrition. It demands an intensive follow-up by an
experienced team and dedicated dietician. Appropriate Phe-free parenteral
nutrition would be necessary especially in case of gastro-intestinal
complications of prematurity.