Mutations causing hereditary hyperphenylalaninemia

Mutations in the genes encoding different parts of phenylalanine hydroxylation system cause persistent hyperphenylalaninaemia. The most frequent form of hyperphenylalaninaemia is caused by mutations in the PAH gene. The most common variant result from defect of tetrahydrobiopterin synthase. Mutations in the PAH and PTS genes in the Polish population are presented. Genotype--phenotype correlations are discussed.