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$Unique_ID{BRK03978}
$Pretitle{}
$Title{McArdle Disease}
$Subject{McArdle Disease Glycogenosis Type V Glycogen Storage Disease Type V
Myophosphorylase Deficiency Forbes Disease Pompe Disease Tarui Disease }
$Volume{}
$Log{}

Copyright (C) 1987, 1989, 1992 National Organization for Rare Disorders,
Inc.

395:
McArdle Disease

** IMPORTANT **
It is possible the main title of the article (McArdle Disease) is not
the name you expected.  Please check the SYNONYMS listing on the next page
to find alternate names, disorder subdivisions, and related disorders
covered by this article.

Synonyms

     Glycogenosis Type V
     Glycogen Storage Disease Type V
     Myophosphorylase Deficiency

Information on the following diseases can be found in the Related
Disorders section of this report:

     Forbes Disease
     Pompe Disease
     Tarui Disease

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 personal physician and/or the agencies listed in the "Resources"
section of this report.

McArdle Disease is a glycogen storage disease.  Symptoms of this
hereditary metabolic disorder are caused by an inborn lack of the enzyme
myophosphorylase.  This enzyme is needed for the breakdown of glycogen (the
body's form of stored energy) into sugar (glucose) in muscle tissues.  In
McArdle Disease the breakdown of glucose cannot take place.  Severe muscle
cramps occur as a result of heavy exercise.

Symptoms

Diagnosis of McArdle Disease usually does not occur before 10 years of age
due to the relatively mild course of the disorder.  Children with McArdle
Disease usually develop normally.  Muscles usually function normally while at
rest or during moderate exercise.  Only during strenuous exercise do severe
muscle cramps occur, usually during late childhood or adolescence.  Myoglobin
(released during muscle breakdown) can often be detected in urine after
strenuous exercise.  In severe cases kidney failure may occur if the
condition is not treated promptly.  The biomedical literature suggests that
an abnormality in oxygen transport to the skeletal muscles may also be
present in individuals with McArdle Disease.

Causes

McArdle Disease is an autosomal recessive genetic disorder.  It is caused by
a lack of the enzyme myophosphorylase.  This enzyme is needed for the
breakdown of stored energy (glycogen) into sugar (glucose).  The lack of
sugar during strenuous exercise causes the severe muscle cramps of McArdle
Disease.  (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 same defective gene from each
parent.  If one receives one normal gene and one gene for the disease, the
person 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 twenty-five 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

All Glycogen Storage Diseases together affect less than 1 in 40,000 persons
in the United States.  Females and males are affected in equal numbers.

Related Disorders

Glycogen Storage Diseases are caused by inborn errors of metabolism in which
the balance between stored energy (glycogen) and available energy (sugar or
glucose) is disturbed.  Too much glycogen tends to be stored in the liver and
muscles and too little sugar is available in the blood.

The following diseases are similar to McArdle Disease.  These can be
compared to McArdle Disease for a differential diagnosis:

Pompe Disease is a hereditary glycogen storage disease.  This hereditary
metabolic disorder is caused by a lack of the enzyme alpha-1,4 glucosidase
(lysosomal glucosidase; acid maltase).  In this disorder, glycogen tends to
accumulate in all body tissues, especially in the heart muscle.

Forbes Disease (Glycogenosis III; Cori Disease) is another glycogen
storage disease inherited through autosomal recessive genes.  Symptoms are
caused by a lack of a debrancher (amylo-1,6 glucosidase) enzyme.  This enzyme
deficiency causes excess amounts of glycogen derived from carbohydrates to be
deposited in the liver, muscles, and heart.  The nerves in the back of the
legs and on the sides of the heel and foot (sural nerves) also tend to
accumulate excess glycogen.  The heart may be involved in some cases.

Tarui Disease (Phosphofructokinase Deficiency) is another type of
glycogen storage disease.  Symptoms of this genetic metabolic disorder are
caused by an inborn lack of the enzyme fructophosphokinase in muscle, and a
partial deficiency of this enzyme in red blood cells.  The deficiency
prevents the breakdown of glucose into energy.  Tarui Disease is
characterized by pain and muscle cramps during muscle stress, but often to a
less severe degree than in McArdle Disease.

For more information on the above disorders, choose "Pompe," "Forbes,"
and "Tarui" as your search terms in the Rare Disease Database.

Therapies:  Standard

Diagnosis of McArdle Disease is made from a history of painful muscle cramps
during exercise, and from functional testing.  Demonstration of a lack of the
enzyme muscle phosphorylase (myophosphorylase) confirms the diagnosis.  The
functional testing consists of a muscle exercise test with blood supply
reduced using a blood pressure cuff.  A failure to see a rise in the blood
lactate, one of the normal breakdown products of glucose in muscle, confirms
the diagnosis of McArdle Disease.

A muscle biopsy (withdrawal of a very small part of a live muscle through
a needle), is performed and tested for myophosphorylase enzyme.
Phosphorylase activity will be lacking or absent in the muscles of a patient
with McArdle Disease.

Treatment usually consists of the avoidance of strenuous exercise.
Variable results have been obtained with oral glucose and fructose treatment.

For women with McArdle Disease who need a Caesarean section during
delivery, special consideration should be given to appropriate anesthesia.

Therapies:  Investigational

Dr. Y.T. Chen at Duke University Medical Center, at the request of the
Glycogen Storage Disease Association, is collecting DNA from patients with
Glycogen Storage Disease Type I to form a DNA bank for GSDI.  Interested
patients may contact the Glycogen Storage Diseases Association for further
information.  The address and phone number of the organization are listed in
the Resources section of this report.

Clinical trials are underway to study the role of NH3 in ventilary
control during exercise.  Interested persons may wish to contact:

     David M. Systrom, M.D.
     Pulmonary & Critical Care Unit
     Massachusetts General Hospital
     Boston, MA  02114
     [phone]

to see if further patients are needed for this research.

This disease entry is based upon medical information available through
January 1992.  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 McArdle Disease, please contact:

     National Organization for Rare Disorders (NORD)
     P.O. Box 8923
     New Fairfield, CT  06812-1783
     [phone]

     Association for Glycogen Storage Diseases
     Box 896
     Durant, IA  52747
     [phone]

     National Digestive Diseases Information Clearinghouse
     Box NDDIC
     Bethesda, MD  20892
     [phone]

     Research Trust for Metabolic Diseases in Children
     Golden Gates Lodge, Weston Rd.
     Crewe CW1 1XN, England
     Telephone:  [phone]

For genetic information and genetic counseling referrals, please contact:

     March of Dimes Birth Defects Foundation
     1275 Mamaroneck Avenue
     White Plains, NY  10605
     [phone]

     Alliance of Genetic Support Groups
     35 Wisconsin Circle, Suite 440
     Chevy Chase, MD  20815
     (800) 336-GENE
     [phone]

References

CECIL TEXTBOOK OF MEDICINE, 18th ed.:  James B. Wyngaarden, and Lloyd H.
Smith, Jr., Eds.:  W.B. Saunders Co., 1988.  Pp. 1135.

THE MERCK MANUAL 15th ed:  R. Berkow, et al:  eds; Merck, Sharp & Dohme
Research Laboratories, 1987.  Pp. 2078.