SLC22A5 and systemic primary carnitine deficiency disease: As one of the four etiological factors of LSMs, primary carnitine deficiency (PCD) is caused by dysfunctional organic cation/carnitine transporter 2 (OCTN2) due to a mutation in the SLC22A5 gene.[1] The subsequent inability of lipids to fuel as alternative sources of energy can be associated with many metabolic disorders of fatty acids.