Published: September 2015 in Journal of Inherited Metabolic Diseases Reports
Article: Should extra phenylalanine be given to children with Tyrosinemia type 1?
Authors: D van Vliet, E van Dam, M van Rijn, TG Derks, G Venema-Liefaard, MM Hitzert, RJ Lunsing, MR Heiner-Fokkema, FJ van Spronsen
Contact: Danique van Vliet
Link to article: ncbi.nlm.nih.gov

This article describes 2 patients with Tyrosinemia type 1 who were treated with NTBC and diet shortly after birth. Patient 1 developed growth retardation, developmental delay and eczema. With the NTBC and dietary treatment, tyrosine concentrations were usually within the treatment range, but phenylalanine concentrations were sometimes severely low.

When the child was 6 months old, extra phenylalanine was given to increase the phenylalanine concentrations. All symptoms disappeared within a very short period. It was thought that the low phenylalanine concentrations were the cause of the different clinical problems the patient experienced. Patient 2 started with the phenylalanine supplementation almost immediately after birth. This mostly prevented the phenylalanine concentrations from getting too low. However, tyrosine concentrations were usually higher in this patient compared to patient 1. This patient did not show any growth, developmental and skin problems.

These examples show that you should not only focus on tyrosine concentrations. Phenylalanine concentrations have to be taken into account in the management of the disease. Giving phenylalanine supplementation has to be considered when phenylalanine concentrations are low. This study did not prove if there is a causal relationship between the clinical symptoms and the low phenylalanine concentrations. Lower limits of phenylalanine concentrations and practical things, for example when and how much phenylalanine supplementation should be given, are not yet known. This requires further study by our own center and in other centers. By publishing this experience, the paper shows the importance of early presentation so that others can learn from this. Most clinicians agree that low phenylalanine concentrations should be prevented.