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$Unique_ID{BRK03983}
$Pretitle{}
$Title{Medium-Chain Acyl CoA Dehydrogenase Deficiency}
$Subject{Medium-Chain Acyl CoA Dehydrogenase Deficiency Acyl CoA Dehydrogenase
Deficiency, Medium-Chain Nonketotic Carnitine Deficiency Carnitine Deficiency
MCAD Deficiency MCADH Deficiency Dicarboxylicaciduria Glutaricaciduria II Reye
Syndrome }
$Volume{}
$Log{}
Copyright (C) 1988, 1989 National Organization for Rare Disorders, Inc.
585:
Medium-Chain Acyl CoA Dehydrogenase Deficiency
** IMPORTANT **
It is possible that the main title of this article (Medium-Chain Acyl CoA
Dehydrogenase Deficiency) is not the name you expected. Please check the
SYNONYM list to find the alternate names and disorder subdivisions covered by
this article.
Synonyms
Acyl CoA Dehydrogenase Deficiency, Medium-Chain
Nonketotic Carnitine Deficiency
Carnitine Deficiency
MCAD Deficiency
MCADH Deficiency
Dicarboxylicaciduria
Information on the following disorders can be found in the Related
Disorders section of this report:
Glutaricaciduria II
Reye Syndrome
General Discussion
** REMINDER **
The information contained in the Rare Disease Database is provided for
educational purposes only. It should not be used for diagnostic or treatment
purposes. If you wish to obtain more information about this disorder, please
contact your physician and/or the agencies listed in the "Resources" section
of this report.
Medium-Chain Acyl CoA Dehydrogenase Deficiency (MCAD) is a metabolic
disorder characterized by a deficiency of the enzyme medium chain CoA
dehydrogenase which is needed for the breakdown of medium chain fatty acids.
This enzyme plays a central role in the metabolism of fats. Low blood sugar
(hypoglycemia), lack of energy (lethargy) and possibly coma, as well as fatty
changes in the liver, may also occur. During hypoglycemic periods, tests
usually show massive amounts of dicarboxylic acid in the urine.
Symptoms
Medium-Chain Acyl CoA Dehydrogenase Deficiency is a form of organic acidemia.
It is characterized by intermittent low blood sugar levels (hypoglycemia)
after fasting, as well as fatigue, and sometimes coma. During periods of
hypoglycemia, tests usually show excessive amounts of dicarboxylic acids in
the urine of 6 to 8 carbon atoms in length. The chemical compound
suberylglycine appears to be diagnostic for this condition. Fatty changes in
the liver may also occur. Symptoms first appear during childhood or early
adolescence.
Causes
CoA Dehydrogenase Deficiency is a hereditary disorder transmitted through
autosomal recessive genes. (Human traits, including the classic genetic
diseases, are the product of the interaction of two genes for that condition,
one received from the father and one from the mother. In recessive
disorders, the condition does not appear unless a person inherits the
defective gene for the same trait from each parent. If a person receives one
normal gene and one gene for the disease, he or she will be a carrier for the
disease, but usually will show no 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 will be
carriers, but healthy as described above. Twenty-five percent of their
children will receive both normal genes, one from each parent, and will be
genetically normal.)
Affected Population
Medium-Chain Acyl CoA Dehydrogenase Deficiency has an incidence of about 1 in
10,000 live births. It first appears during infancy and early childhood and
males and females are affected in equal numbers.
Related Disorders
Symptoms of the following disorders are similar to those of Medium-Chain Acyl
CoA Dehydrogenase Deficiency. Comparisons may be useful for a differential
diagnosis:
Glutaricaciduria II: There are two forms of this disorder which occur
during different stages of life. They are both forms of organic acidemias
which are a group of metabolic disorders characterized by excess acid in the
blood and urine.
1) Glutaricaciduria IIA (GA IIA). This neonatal form of Glutaricaciduria
II is a very rare, sex-linked hereditary disorder characterized by large
amounts of glutaric and other acids in blood and urine. Some researchers
believe the disorder is caused by a defect in the breakdown of acyl-CoA
compounds.
2) Glutaricaciduria IIB (GA IIB; Ethylmalonic Adipicaciduria) is the
milder, adult form of Glutaricaciduria II. This disorder, inherited through
autosomal recessive genes, is characterized by acidity of the body tissues
(metabolic acidosis), and a low blood sugar level (hypoglycemia) without an
elevated level of ketones in body tissues (ketosis). Large amounts of
glutaric acid in the blood and urine are caused by a deficiency of the enzyme
"Multiple acyl-CoA dehydrogenase". (For more information, choose
"Glutaricaciduria II" as your search term in the Rare Disease Database.)
Reye Syndrome is a combination of acute brain disease (encephalopathy)
and fatty degeneration of the abdominal organs. This disorder tends to
follow some acute viral infections such as flu or chicken pox in combination
with certain toxic substances such as aspirin. In addition to these viruses
and toxins, deficiencies of the enzymes needed in the breakdown of ammonia to
urine appear to be a contributing factor. Symptoms occur suddenly and
progress quickly, leading to coma. (For more information, choose "Reye" as
your search term in the Rare Disease Database.)
Therapies: Standard
Symptoms of Medium-Chain Acyl CoA Dehydrogenase Deficiency may be prevented
by not allowing children with this deficiency to fast for prolonged periods
of time. Sometimes children have to be awakened at night for feedings.
Others may be fed intravenously or parenterally overnight. The usefulness of
restricting the amino acids lysine, hydroxylysine and tryptophan (which
generate glutaric acid when they are metabolized) is not established at the
present time. Acute episodes of acidity in blood and body tissues (acidosis)
and dehydration are treated with fluids and bicarbonate. Many of the adverse
effects of organic acidemias are due to secondary carnitine depletion. Such
patients should have plasma carnitine measured and, if deficient, begin a
supplement of 100-300 mg/kg/day of oral l-carnitine. Other treatment is
symptomatic and supportive.
Therapies: Investigational
This disease entry is based upon medical information available through
December 1989. Since NORD's resources are limited, it is not possible to
keep every entry in the Rare Disease Database completely current and
accurate. Please check with the agencies listed in the Resources section for
the most current information about this disorder.
Resources
For more information on medium Chain Acyl CoA Dehydrogenase Deficiency,
please contact:
National Organization for Rare Disorders (NORD)
P.O. Box 8923
New Fairfield, CT 06812-1783
(203) 746-6518
Support Group for Medium Chain Acyl CoA Dehydrogenase Deficiency (MCAD)
805 Montrose Dr.
Greensboro, NC 27410
(919) 547-0196
Organic Acidemia Association
522 Lander St.
Reno, NV 89512
(702) 322-5542
British Organic Acidemia Association
5 Saxon Rd.
Ashford, Middlesex TW15 1QL
England
National Digestive Diseases Information Clearinghouse
Box NDDIC
Bethesda, MD 20892
(301) 468-6344
Research Trust for Metabolic Diseases in Children
Golden Gates Lodge, Weston Rd.
Crewe CW1 1XN, England
Telephone: (0270) 250244
For information on genetics and genetic counseling referrals, please
contact:
March of Dimes Birth Defects Foundation
1275 Mamaroneck Avenue
White Plains, NY 10605
(914) 428-7100
Alliance of Genetic Support Groups
35 Wisconsin Circle, Suite 440
Chevy Chase, MD 20815
(800) 336-GENE
(301) 652-5553
References
MENDELIAN INHERITANCE IN MAN, 7th ed.: Victor A. McKusick; Johns Hopkins
University Press, 1986. Pp. 800-801.
THE METABOLIC BASIS OF INHERITED DISEASE, 5th ed.: John B. Stanbury, et
al., eds; McGraw Hill, 1983. P. 238.
CATALYTIC DEFECT OF MEDIUM-CHAIN ACYL COENZYME A DEHYDROGENASE
DEFICIENCY: LACK OF BOTH COFACTOR RESPONSIVENESS AND BIOCHEMICAL
HETEROGENEITY IN EIGHT PATIENTS: B.A. Amendt, et al.; J Clin Investi (1985:
issue 76). Pp. 963-969.
DICARBOXYLIC ACIDURIA: DEFICIENT 1-(14)C-OCTANOATE OXIDATION AND MEDIUM-
CHAIN ACYL-CoA DEHYDROGENASE IN FIBROBLASTS: W.J. Rhead, et al.; Science
(1983: issue 221). Pp. 73-75.