Carnitine deficiency syndromes manifested as metabolic encephalopathy, lipid storage myopathy, or cardiomyopathy are reviewed from the Department of Pediatrics, Park Nicollet Medical Center, Minneapolis, MN. Carnitine deficiency may be primary and caused by impaired renal conservation, or secondary to various inborn errors of metabolism that promote excretion of carnitine as acylcarni tine. The genetic defects of intermediary metabolism with secondary systemic carnitine deficiency include: 1) Acyl-CoA dehydrogenase deficiencies; 2) organic acidemias; 3) mitochondrial respiratory disorders; and 4) carnitine octanoyltransferase deficiency. Other disorders with secondary carnitine deficiency include Reye syndrome, valproate-induced, renal Fanconi, chronic renal failure with hemodialysis, parenteral nutrition in premature infants, Kwashiorkor, cirrhosis, severe myopathies, myxedema, adrenal insufficiency, hypopituitarism and pregnancy. Systemic carnitine deficiency was first described in an 11 year old male with recurrent attacks resembling Reye syndrome from the age of three, and progressive muscle weakness from the age of ten. Metabolic encephalopathy is a frequent mode of presentation and the acute encephalopathic crises of systemic carnitine deficiency present with vomiting, progressive deterioration of consciousness, hepatomegaly, hypoglycemia, hyperammonemia, increased transaminase and hypoprothrombinemia. Acute crises produced by carnitine deficiency are treated with intravenous glucose supplementation to correct hypoglycemia. When hyperammonemia is present protein intake is restricted. Organic acidemias are treated with dietary modifications and/or vitamin supplementation. Frequent meals of high carbohydrate content and a low fat diet are advisable in all patients with carnitine deficiency. Maintenance therapy consists of L-carnitine 100 mg/ kg/daily in infants and children. There are no known serious side effects of L-carnitine. [1]