The best results have been obtained in urea cycle disorders (Stéphenne et al 2005, 2006; Meyburg et al 2009b; Pareja et al 2013), in Crigler–Najjar syndrome (Lysy et al 2008a; Fox et al 1998; Pareja et al 2013; Ambrosino et al 2005), infantile Refsum’s disease (Sokal et al 2003), factor VII deficiencies (Dhawan et al 2004), phenylketonuria (Stéphenne et al 2012), glycogen storage disease type I (Pareja et al 2013; Muraca et al 2002), Refsum disease (Sokal et al 2003) and tyrosinemia (Pareja et al 2013). This evidence concerns the gene F7 and Refsum disease.