SLC22A5 and renal tubule disorder: Other causes of carnitine deficiency besides mutations in the SLC22A5 gene are classified as secondary carnitine deficiency and include other hereditary metabolic diseases (e.g., fatty acid oxidation defects), medication (valproic acid, cyclosporine, and pivampicillin), malnutrition, hemodialysis and renal tubular dysfunction (Fanconi nephropathy), and prematurity (lower placentary transfer).