SLC22A5 and systemic primary carnitine deficiency disease: To date, the carnitine deficiency phenotype was observed in the context of (a) primary carnitine deficiency resulting from inactivating mutations in Octn2 gene, (b) secondary carnitine deficiency that may be caused by different metabolic abnormalities all ultimately leading to the loss of carnitine in the urine, and (c) patients with CKD undergoing hemodialysis and losing carnitine through the dialysis membrane (reviewed in ref. 55).