Glutaryl-CoA dehydrogenase (EC 1.3.99.7) deficiency, glutaric aciduria type 1 (GDH deficiency, McKusick 231670), is an autosomal recessively inherited inborn error of the metabolism of the amino acids lysine, hydroxylysine and tryptophan (Goodman and Frerman 1989). Most of the patients suffer from a severe neurological disease with choreoathetosis and dystonia, but children and adults with the enzymatic deficiency and no symptoms at all have also been reported (Amir et al 1989). Refsum disease (McKusick 266500) is a recessively inherited autosomal disease affecting the oxidation of phytanic acid. If untreated, the patients accumulate high amounts of phytanate in their triglycerides and other lipids