Specific mutations in the gene encoding phenylalanine hydroxylase (PAH), located on chromosome 12q22-24.1, are linked to tetrahydrobiopterin (BH4; sapropterin)-responsive phenylketonuria (PKU). Diagnosis is usually done through the newborn screening for PKU, followed by a BH4 loading test. So far, more than 60 mutant alleles, presenting with a substantial residual PAH activity (average approxim...

Since the cloning of the cystic fibrosis transmembrane regulator (CFTR) protein in the late 1980s and subsequent significant advances in understanding the pathophysiology of cystic fibrosis (CF) there have been high expectations that transformative, disease-modifying therapies could be developed. 2 Dysfunction of the CFTR protein results in significant reduction or absence of chloride transport...