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Carnitine Deficiency Syndrome

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Synonyms of Carnitine Deficiency Syndrome

Disorder Subdivisions

General Discussion

Carnitine Deficiency Syndrome is a rare metabolic disorder that may be inherited in some cases, or occur as a result of other metabolic disorders. Carnitine functions in the body as a carrier of fatty acids to the energy centers in muscles (mitochondria). A deficiency of carnitine, normally produced by the liver and kidneys, can result in extreme muscle weakness and other related symptoms.

Symptoms

There may be two types of Carnitine Deficiency: Myopathic Carnitine Deficiency (affecting muscles) and Systemic Carnitine Deficiency (affecting the entire body).

Muscle weakness is the primary symptom of Myopathic Carnitine Deficiency Syndrome. Shortages and/or interrupted supplies of energy to muscles may result in the destruction of muscle tissue. Oxygen-carrying protein (myoglobulin) may also be lost and secreted in the urine (rhabdomyolyis).

Systemic Carnitine Deficiency Syndrome differs from Myopathic Carnitine Deficiency because low levels of carnitine are found in tissues other than muscles, including blood and/or urine. There may also be a deficiency of carnitine in the central nervous system, liver, and/or heart. Symptoms may include loss of brain tissue (degenerative encephalopathy), episodes of vomiting, confusion, and/or stupor that progresses to coma.

Carnitine Deficiency Syndrome may also be associated with low blood sugar (hypoglycemia). Damage to the heart muscle may result in chronic heart disease (cardiomyopathy).

Causes

The Carnitine Deficiency Syndromes may be classified as primary or secondary. When a person is thought to have no other underlying disease that could cause low levels of carnitine, then the deficiency is termed "primary." When the deficiency is caused by another underlying disorder, then it is said to be "secondary."

In some cases of this disorder, total carnitine levels may be normal but are nonetheless insufficient to meet metabolic needs because of the presence of another associated disorder.

Primary Carnitine Deficiency Syndrome is thought to be inherited as an autosomal recessive genetic trait. Human traits, including the classic genetic diseases, are the product of the interaction of two genes, one received from the father and one from the mother. In recessive disorders, the condition does not appear unless a person inherits the same defective gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk of transmitting the disease to the children of a couple, both of whom are carriers for a recessive disorder, is 25 percent. Fifty percent of their children risk being carriers of the disease, but generally will not show symptoms of the disorder. Twenty-five percent of their children may receive both normal genes, one from each parent, and will be genetically normal (for that particular trait). The risk is the same for each pregnancy.

Secondary Carnitine Deficiency usually occurs as a symptom of metabolic disorders such as organic acidemias. In rare cases, Carnitine Deficiency may also occur when there is severe liver disease or kidney (renal tubular) malfunction.

Affected Populations

Primary Carnitine Deficiency Syndrome is a rare disorder that affects males and females in equal numbers. There are only a few hundred patients in the United States with Primary Carnitine Deficiency. People who have any of the organic acidemias, mitochondrial disorders, severe liver disease, and/or renal tubular dysfunction may be at risk of developing Secondary Carnitine Deficiency.

Related Disorders

Symptoms of the following disorders can be similar to those of Carnitine Deficiency Syndrome. Comparisons may be useful for a differential diagnosis:

Isovaleric Acidemia is a rare inherited metabolic disorder (organic acidemia) of infancy characterized by attacks of vomiting, lack of appetite, and fatigue. Infants with this disorder become progressively weak and often have abnormally low body temperatures (hypothermia). A strong offensive body odor is also associated with this disorder. (For more information on this disorder, choose "Isovaleric Acidemia" as your search term in the Rare Disease Database.)

Propionic Acidemia is another form of organic acidemia that occurs in infancy. It is caused by a deficiency of the enzyme propionyl-CoA carboxylase (PCC). The initial symptoms of Propionic Acidemia include failure to thrive, vomiting, and extreme fatigue. Children who are very ill may have a better response to L-carnitine administered intravenously.

Mitochondrial Cytopathies are a group of disorders that affect the ability of the body's cells to turn food into energy. Without sufficient energy, cells may be unable to function properly. Furthermore, incompletely metabolized food byproducts may accumulate and act as poisons within the body. These disorders are caused by a malfunction in one of five enzymes, referred to as complexes I, II, III, IV, and V. They may involve only one or several organs or systems, including the brain, nerves, muscles, and heart, and their effects range greatly in severity.

Standard Therapies

The orphan drug L-carnitine (Carnitor) is available in tablet and liquid form. It is manufactured by Sigma Tau Pharmaceuticals. For more information on this drug, contact:

Sigma-Tau Inc.
800 South Frederick Avenue
Suite 300
Gaithersburg, MD 20877
(800) 447-0169
(301) 948-1041

Investigational Therapies

Coenzyme Q10, a vitamin-like substance, is being studied as a possible treatment for mitochondrial disorders. More studies are needed to determine the long-term safety and effectiveness of this treatment.

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: prpl@cc.nih.gov

For information about clinical trials sponsored by private sources, contact:
www.centerwatch.com

Organizations related to Carnitine Deficiency Syndrome

References

TEXTBOOK
Birth Defects Encyclopedia: Mary Louise Buyse, Editor-In-Chief; Blackwell Scientific Publications, 1990. P. 1200.

Cecil Textbook of Medicine, 20th Ed.: J. Claude Bennett and Fred Plum, Editors; W.B. Saunders Co., 1996. P. 2166.

Harrison's Principles of Internal Medicine, 14th Ed.: Kurt J. Isselbacher, M.D. et al., Editors; McGraw-Hill, Inc., 1998. Pp. 2478-79.

The Merck Manual, 17th Ed.: Robert Berkow and Mark Beers, Editors; Merck Research Laboratories; 1999. P. 32.

Nelson Textbook of Pediatrics, 15th Ed.: Richard E. Behrman, Editor; W.B. Saunders Company, 1996. P. 1755.

Principles of Neurology, 6th Ed.: Raymond D. Adams, Maurice Victor, and Allan A. Ropper, Editors; McGraw-Hill, Inc., 1997. Pp. 1437-38.

The Metabolic Basis of Inherited Disease, 6th Ed.: Charles R. Scriver, et al., Editors; McGraw Hill, 1989. Pp. 868-898.

ARTICLE
Carnitine Deficiency Syndromes. G.N. Breningstall; Pediatr Neurol (Mar-Apr 1990; 6(2)). Pp. 75-81.

Carnitine: Metabolism and Clinical Chemistry. N. Siliprandi et al.; Clin Chim Acta (Jul 31 1989; 183(1)). Pp. 3-11.

Decreased Fasting Free Fatty Acids with L-Carnitine in Children with Carnitine Deficiency. W.F. Schwenk et al.; Pediatr Res (May 1988; 23(5)). Pp. 491-94.

Transport of Carnitine into Cells in Hereditary Carnitine Deficiency. B.O. Eriksson et al.; J Inherited Metab Dis (1989; 12(2)). Pp. 108-11.

Carnitine Metabolism and Deficiency Syndromes. C. J. Rebouche et al.; Mayo Clin Proc (Aug 1983; 58(8)). Pp. 533-40.

Mitochondrial Cytopathies Disorders of Oxidative Phosphorylation and Beta-Oxidation Primer: Diagnosis and Principles of Management. B.H. Cohen; Mitochondrial News (Fall 1997; 2(3)). Pp. 1, 6-9.

Angelini C, Vergani L, Martinuzzi A: Clinical and biochemical aspects of carnitine deficiency and insufficiency: transport defects and inborn errors of beta-oxidation. Crit Rev Clin Lab Sci 1992; 29(3-4): 217-42.

Bok LA, Vreken P, Wijburg FA, et al: Short-chain Acyl-CoA dehydrogenase deficiency: studies in a large family adding to the complexity of the disorder. Pediatrics 2003 Nov; 112(5): 1152-5.

Bonner CM, DeBrie KL, Hug G, et al: Effects of parenteral L-carnitine supplementation on fat metabolism and nutrition in premature neonates. J Pediatr 1995 Feb; 126(2): 287-92.
Borum PR: Carnitine in neonatal nutrition. J Child Neurol 1995 Nov; 10 Suppl 2: S25-31De Vivo D, Tein I: Primary and secondary disorders of carnitine metabolism. International Pediatrics 1990; 5: 134-41.

Koizumi A, Nozaki J, Ohura T, et al: Genetic epidemiology of the carnitine transporter OCTN2 gene in a Japanese population and phenotypic characterization in Japanese pedigrees with primary systemic carnitine deficiency. Hum Mol Genet 1999 Nov; 8(12): 2247-54

FROM THE INTERNET
Online Mendelian Inheritance in Man (OMIM). Victor A. McKusick, Editor; Johns Hopkins University, Last Edit Date 5/25/99, Entry Number 212140.

Report last updated: 2009/04/08 00:00:00 GMT+0