The human SLC22A5,15 and 16 genes encode for sodium-dependent, high affinity carnitine cotransporters which maintain systemic and tissue concentrations of carnitine. Carnitine is essential for beta-oxidation of long-chain fatty acids to produce ATP. SLC22A5 encodes the organic cation/carnitine transporter 2 (OCTN2). SLC22A5 is strongly expressed in the kidney, skeletal muscle, heart and placenta. Defects in SLC22A5 are the cause of systemic primary carnitine deficiency (CDSP; MIM:212140), an autosomal recessive disorder of fatty-acid oxidation caused by defective carnitine transport resulting in cardiac, skeletal, or metabolic symptoms. If diagnosed early, all clinical symptoms can be completely reversed with a carnitine supplement. However, if left untreated, patients will develop lethal heart failure (Shibbani et al. 2014, Tamai 2013).