Disorders of phenylalanine and tyrosine metabolism

Abstract

This article provides a review of the inborn errors of phenylalanine and tyrosine metabolism including the diagnostic approach, dietary and pharmalogical management and emerging therapies. Hyperphenylalaninaemia results mainly from defects in either phenylalanine hydroxylase (PAH) (resulting in phenylketonuria (PKU)) or the production or recycling of tetrahydrobiopterin (BH4). Untreated PKU results in irreversible neurocognitive impairment. Five inherited disorders of tyrosine metabolism are known, which include tyrosinemia type I, type II, type III, hawkinsinuria and alkaptonuria. Newborn screening for these disorders has enabled their early detection and decreased the associated morbidity and mortality.