[Carnitine deficiency].

Carnitine facilitates the transport of activated fatty acids across the mitochondrial membrane and regulates energy metabolism through regeneration of intramitochondrial coenzyme A. In carnitine deficiency it may be a limiting factor for fatty acid oxidation and ketogenesis. Primary myopathic carnitine deficiency is characterized by low carnitine concentrations usually restricted to muscle; whereas systemic carnitine deficiency shows decreased concentrations in other organs and plasma as well. The latter condition features recurrent metabolic crises similar to those seen in Reye's syndrome and nonketotic hypoglycemia. A therapy with L-carnitine should be undertaken, but does not always prove effective. Similar symptoms may be caused by defects in beta-oxidation, Krebs cycle or respiratory chain enzymes. The conditions may be associated with secondary carnitine deficiency. Patients with organic acidurias exhibit an increased excretion of carnitine esters and an insufficiency of free carnitine. Carnitine supplementation may ameliorate the metabolic disturbance. Secondary carnitine deficiency has also been described in patients receiving chronic valproic acid therapy. Hemodialysed chronic renal patients may benefit from L-carnitine therapy and show improvement of their hyperlipidemia. Nutritional carnitine deficiency can be primarily expected in premature infants receiving a carnitine free diet, since these infants have an impaired capacity for carnitine biosynthesis.