SLC22A5 and systemic primary carnitine deficiency disease: Primary carnitine deficiency (PCD, OMIM 212140) refers to an autosomal recessive disorder of fatty acid oxidation caused by mutations in the SLC22A5 gene, which encodes the organic cation transporter 2 (OCTN2) (Tang et al., 1999; Cederbaum et al., 2002).