The prospect of a muscle disease is worrisome to many people because
they are afraid of becoming immobile. Yet in many cases, treatment exists
for myopathy (muscle disease). Proper diagnosis and therapy increase the
chances of living life fully in spite of myopathy.
What myopathies are
Myopathy is the medical term for muscle disease. There are many causes
of muscle disease, such as infection, muscle injury due to medications,
inherited diseases affecting muscle function, disorders of electrolyte
levels, and thyroid disease. Some of these disorders, such as polymyositis,
dermatomyositis and inclusion body myositis, develop when the immune system
attacks muscles. This inflammation damages muscle tissue and makes them
weak.
Patients with myopathy develop weakness in the large muscles around the
neck, shoulders and hips. This causes difficulty in climbing stairs, getting
up from a chair or toilet seat, or reaching for objects overhead. Most
patients have little if any pain in their muscles, which distinguishes
them from patients with other forms of muscle disease, from those who
have joint pain due to arthritis, and from those with numbness or tingling
in their hands and feet due to neurological problems. Many patients with
other conditions complain of weakness, but when questioned closely, they
really mean that they are tired, short of breath or depressed rather than
suffering from true muscle weakness.
Some patients with myopathy develop weakness of throat muscles involved
in swallowing, and this may cause choking or aspiration (intake) of food
into the lungs when eating. Others may experience shortness of breath
and cough due to inflammation of the lungs.
Polymyositis is an inflammation of the muscle tissue that leads to weakness.
Dermatomyositis is characterized by immune inflammation of muscles as
well as by the presence of a rash. This rash, which appears as a purple
or red discoloration of the upper eyelids, is present in almost all children
with inflammatory myopathy. Scaly red lesions over the back of the fingers
at the knuckles or over the elbows or knees may also occur. Occasionally
patients can develop the rash with no evidence of muscle disease, a condition
which is known as “amyopathic dermatomyositis.” People with Dermatomyositis
may also have lung inflammation (pneumonitis), and children may have an
inflammation of the blood vessels (vasculitis) and calcium deposits in
the skin referred to as calcinosis.
Who gets myopathies
The inflammatory myopathies are rare diseases. Polymyositis
and dermatomyositis occur in approximately 1 person per 100,000. All age
groups are affected with peak incidence between the ages of 5 and 10 in
children, and between 40 and 50 in adults. Women are affected about twice
as often as men. All ethnic groups are affected. It is not possible to
predict who will develop an inflammatory myopathy.
Inclusion body myositis is also a very rare disease, but differs from
the other inflammatory myopathies in that men are affected more commonly
than women, and the patients tend to be older.
What causes myopathies
It is not known what causes the idiopathic inflammatory myopathies. A
leading theory is that abnormalities in the body's immune system may lead
to the development of inflammation and subsequent damage to muscle cells
or the blood vessels that are in the muscle.
|
Fingers of a person with
dermatomyositis show red bumps on the knuckles (Gottron's papules),
redness around the nails, and prominent cuticles. |
How myopathies are diagnosed
A diagnosis of myopathy is suspected when patients complain of difficulty
performing tasks that require muscle strength or when they develop certain
rashes or respiratory problems. To establish a diagnosis, a muscle strength
examination will be performed to determine if true muscle weakness is
present. This likely will be followed by a blood test to measure the level
of various muscle enzymes, an electromyogram to gauge electrical activity
in muscle, and finally a biopsy of a weak muscle. Sometimes MRI scanning
can help to establish the presence of abnormal muscle. Blood may also
be tested for the presence of myositis-specific antibodies (immune proteins),
which help to establish a diagnosis and give some information about prognosis.
Inclusion body myositis is diagnosed by the presence of specific changes
on the muscle biopsy.
How myopathies are treated
Treatment depends on the type of myopathy diagnosed.
Polymyositis and dermatomyositis are usually treated with medications.
An oral corticosteroid such as prednisone (Deltasone and others)
is usually administered in high doses once the diagnosis has been established.
Blood muscle enzymes usually return to normal in about 4 to 6 weeks and
patients gradually regain strength in 2 to 3 months. Methotrexate or
azathioprine are usually
added to ensure better long term control of the disease and to avoid long
term side effects of cortisone such as weight gain and redistribution
of body fat, thinning of the skin, osteoporosis, cataracts and even muscle
weakness. In severe or treatment-resistant cases additional measures may
include intravenous immunoglobulin and other immunosuppressive medications
including cyclosporine (Neoral, Sandimmune),
tacrolimus (Prograf) or mycophenolate (Cellcept).
Unfortunately there is no dependably effective treatment for inclusion
body myositis. Patients may be given a trial course of prednisone followed
by methotrexate or azathioprine. However, if there is no improvement in
2 to 3 months, all drugs should be discontinued.
Patients with dermatomyositis and rash should protect themselves from
the sun by limiting time outdoors and using sunscreen when they do go
outside. This is because the rash worsens after sun exposure, for reasons
that are unclear.
Physical therapy and exercise are important in the treatment of myopathy.
Severely weak patients who are confined to their beds should receive range
of motion exercises to prevent joint contractures (distortion or deformity
of the joint). Patients with moderate weakness should begin a muscle-strengthening
program that gradually increases in intensity as strength is regained.
Mildly weak patients should be encouraged to participate in normal activities.
Patients with swallowing difficulties should receive appropriately prepared
food and should be positioned in bed to prevent choking. Patients being
treated with prednisone are at risk for the development of osteoporosis
and should receive appropriate preventive treatment.
 |
| Physical therapy can help patients continue to lead active lives. |
Broader health impacts of myopathies
In adults, dermatomyositis and to a lesser extent polymyositis at times
may be related to an underlying cancer. Therefore all adult patients with
these disorders should receive appropriate testing to rule out cancer.
Living with myopathy
Since the myopathies are chronic diseases, it is important for patients
to practice good general health measures including a well-balanced nutritional
diet, maintenance of normal weight and proper management of any other
chronic illnesses. As discussed above, regular exercise is important to
regain and maintain strength. It is important for employers, teachers
and family members to understand the limitations imposed by muscle weakness
in myopathy patients, particularly since they may look entirely normal.
Points to remember
Myopathy almost always causes loss of muscle strength. Some patients
develop rashes or breathing problems. While the myopathies cannot be cured,
most can be effectively treated. Early diagnosis and adherence to the
treatment plan are important.
The role of a rheumatologist in the treatment
of myopathies
Myopathies should be accurately diagnosed to ensure the best possible
outcomes. Rheumatologists are specialists in musculoskeletal disorders
and therefore are more likely to make a proper diagnosis. They can also
advise patients about the best treatment options available.
To find a rheumatologist
For a listing of rheumatologists in your area, click
here.
Learn more about rheumatologists and rheumatology
health professionals.
For more information:
The American College of Rheumatology has compiled this list to give you
a starting point for your own additional research. The ACR does not endorse
or maintain these Web sites, and is not responsible for any information
or claims provided on them. It is always best to talk with your rheumatologist
for more information and before making any decisions about your care.
The Arthritis Foundation
www.arthritis.org
National Institute of Arthritis and Musculoskeletal and Skin Diseases
Information Clearinghouse
www.niams.nih.gov
The Myositis Association of America
http://www.myositis.org/
Specific information about particular myopathies:
http://www.ninds.nih.gov/health_and_medical/disorders/polymyos_doc.htm
http://www.emedicine.com/emerg/topic474.htm
http://www.ninds.nih.gov/health_and_medical/disorders/inclusion_doc.htm
Updated: April 2004
Author: This information was written by Marc Miller, MD, and reviewed
by the American College of Rheumatology Communications and Marketing Committee.
