Myositis involves the inflammation of our muscles, and we have two types of muscles: voluntary and involuntary. The voluntary (or "skeletal") muscles enable us to move our arms and legs. The involuntary muscles are in our blood vessels and gastrointestinal tract. Although any muscle can be affected by myositis, the disease largely affects the voluntary muscles.
How are muscles damaged in myositis?
Myositis literally means muscle inflammation. Dermatomyositis means inflammation of the skin and muscles. Together, they are called inflammatory myopathies. When skin or muscle tissue is inflamed, it has been infiltrated by white blood cells called lymphocytes.
Lymphocytes are the police force of the body's immune system. They are supposed to protect our body from foreign invaders, such as bacteria and viruses. They constantly patrol the body, on the lookout for things that "don't look right." When an area of the body is infected, white blood cells are signaled. They can multiply and head for the infected tissue to attack and remove the invaders.
However, in inflammatory myopathies, lymphocytes also infiltrate healthy muscle fibers. This infiltration causes inflammation. It damages healthy tissue. Eventually, it can destroy muscle fibers. After the fibers are destroyed, scar tissue replaces healthy tissue, and there is no longer function in that muscle tissue. When skin is attacked, rashes may occur.
Not every muscle is attacked at once by lymphocytes. That's why, depending on whether or not the particular muscle being examined is inflamed, a myositis patient may have a normal muscle biopsy.
What lymphocytes are involved?
It is believed that for people with polymyositis, CD-8 lymphocytes are attracted to muscle tissue in this destructive manner. CD-4 lymphocytes are related to the skin. In dermatomyositis, CD-4 lymphocytes are also involved.
Why are lymphocytes getting the wrong "message" and attacking tissue that is not foreign?
It is possible that the lymphocytes are getting the wrong message, and the body's defense plan has gone awry. Or it is possible that the lymphocytes are getting the right message; perhaps there is something in the muscle that the lymphocytes are attracted to, such as a virus, and they are trying to destroy this foreign cell - but healthy tissue gets destroyed at the same time. We don't know precisely the cause of lymphocyte infiltration.
Can muscle tissue regenerate once the scar tissue has moved in?
We all have "satellite cells," which are precursors to muscle cells. As we age, the number of satellite cells is reduced, as are the chances to regenerate new muscle. So, unfortunately, there is little chance for adults to regenerate muscle. That's why therapy is designed to stop further muscle loss, as well as to maximize the muscle fibers still present. Treatments do this by reducing the numbers and activities of lymphocytes.
How can I look "normal" when I feel so sick?
Despite the internal war being waged on muscles, myositis patients may have muscles that appear, on the surface, normal in size. That's because inflammatory cells "take up room" in the muscle mass. So even though you may feel weak, your muscles may appear at first glance to be normal in size. In fact, this is one of signs that doctors use to help diagnose myositis: people who have muscle weakness from nerve damage normally have atrophy (degeneration) together with weakness; people who have myositis may have weakness without atrophy.
What causes difficulty swallowing?
Dysphagia is the medical term for difficulty swallowing. It can arise from several causes. It's important that you and your physician find the cause of your difficulty swallowing - because dysphagia can be dangerous. You must tell your physician promptly if you are having problems swallowing.
The muscles surrounding the esophagus ("food tube") usually propel food down the tube. In dysphagia, muscle dysfunction prevents the food from going down properly. Because your esophagus is so close to your windpipe, complications can be serious and include choking.
To help discern the cause of dysphagia, your doctor may recommend a test called a barium swallow. For some patients, surgical procedures can correct dysphagia.
How long will the disease last?
Doctors do not know. It could be of short duration (one year) or much longer. Because we do not know where the cause arises, it's difficult to tell if the disease is cured or still active.
What does treatment do?
Treatment today focuses on controlling inflammation - reducing the inflammatory cells in muscle and skin tissue, thus preventing or slowing muscle destruction. Some day, when we learn the cause of myositis, we may be able to intervene earlier in the process - stopping whatever triggers the damaging inflammatory process in the first place.
How do corticosteroids work -- and what are their pros and cons?
The most commonly used medications for myositis are corticosteroids, such as prednisone. Our adrenal glands naturally produce corticosteroids (also known as steroids). They were first produced as drugs and used to treat patients with rheumatoid arthritis in the 1940s. At first, they seemed to be "wonder drugs" because they decrease inflammation so dramatically. However, over time, side effects developed. The risk of side effects is dose-related: the more you take -- and the longer you take it -- the greater the risk. Some of steroid side effects are:
- psychological changes (such as mood ups and downs);
- cosmetic changes (such as hair loss, acne, and weight gain);
- insomnia (which is very common and is one of the earlier side effects);
- increased risk of cataracts;
- increased risk of diabetes;
- increased risk of osteoporosis (bone thinning) and avascular necrosis (AVN or bone death).
The amount of steroid our bodies manufacture is based on a delicate balance mechanism. Our pituitary gland senses the amount of steroids in our system -- both what we make and what we may take as pills or injections. The pituitary gland secretes a hormone, called ACTH to stimulate the adrenal cortex to make more cortisone. The pituitary gland shuts off the ACTH production when steroid levels are high. Therefore, discontinuing prednisone suddenly may lead to a complete lack of our own body's steroid-producing ability. This can cause a life-threatening crisis. So steroid doses should always be lowered gradually.
Is it better to take methotrexate in pills or by injection?
There are benefits and drawbacks to each method.
- Methotrexate can be absorbed both orally (by pill) and by injection, but it is more easily absorbed by injection.
- Nausea, a common side effect, may be avoided when methotrexate is injected.
- Theoretically, methotrexate may be more toxic to the liver when taken orally because it goes directly to the liver and then into the blood circulation. When it is injected, methotrexate goes directly into circulation; it is only on the "second pass" that it goes to the liver. However, clinical studies have not proven that injection is safer.
How does gamma globulin help myositis?
Gamma globulin (also known as immunoglobulin) is used to treat patients with a variety of connective tissue disorders. It is given intravenously - also known as IV or into the vein. In some patients, it is quite effective; in others, it does not provide any improvement. Gamma globulin is one of the safest treatments available to myositis patients. However, it may cause such side effects as severe headaches, fever, and chills.
Doctors don't know exactly why gamma globulin works. And they can't predict whether it will be successful for a given individual. When gamma globulin works, it works rapidly. It may allow patients to lower dosages of other medications. But it is very costly, cumbersome, and time consuming to administer. (See Education Programs for a special HSS program - our Infusion Therapy Unit that enables you to have IV gamma globulin on an outpatient basis, without hospitalization.) There is no rigid protocol for administering gamma globulin, and all doctors do not use it in the same way.
What new drugs are being used for myositis?
The newest are etanercept (brand named Enbrel) and infliximab (Remicade). These drugs have been approved by the FDA for the treatment of rheumatoid arthritis but not for myositis. For FDA approval, a lot of research must be done to prove they are safe and effective for myositis. Because myositis is much rarer than rheumatoid arthritis, it will take longer for such research to be done. However, other therapies that were successful for rheumatoid arthritis (such as prednisone, methotrexate, and azathioprine) also, with time, have been shown effective for myositis. So it's not surprising that some doctors have been trying Enbrel and Remicade for myositis -- with good results.
But one serious problem may arise: costs. Many health insurance companies are unwilling to reimburse for these drugs. Usually, they say it's because these medications are not FDA-approved for myositis. Another possible reason is the high cost of these medications. For instance, Enbrel costs about $1,000 per month. Eventually, insurance companies may change their policies if there is good evidence of successful myositis treatment with these medications. That's what has happened with other drugs.
How does the doctor decide if a treatment is effective?
Some of the indicators used are:
- Your own impression of whether you feel better or worse;
- A rash clears up -- or worsens;
- Measures of muscle strength;
- Imaging techniques, such as MRI (magnetic resonance imaging) and sonograms;
- Laboratory measures of CPK levels.
CPK is an enzyme related to energy transfer. When muscle is destroyed, this enzyme leaks out of muscles -- so its level in the blood rises. However, CPK may not be the best measure of myositis because levels vary greatly from one person to the next. If your CPK level varies only slightly, it may not be the best way to measure progress. Genetics, race, gender, and age also influence CPK levels.
Remember that your impressions are critically important. That's why it's important that be ready to tell your doctor what you have been feeling. Keep some type of "symptom diary;" look at it a few days before your appointment to judge the trend of how you have been feeling. Then write down a brief summary. This will help you be ready to discuss your experiences with your doctor.
What is Raynaud's Disease?
Certain types of muscle coat blood vessels and control their size. Muscle action can switch off the flow of blood to certain regions of the body when necessary. One of the times this is necessary is in cold weather. The brain needs a certain warmth to operate. So when hands and feet get cold, blood vessels in the hands and feet constrict to prevent cold blood from entering the general circulation and reaching the brain.
In people with Raynaud's, this decreased blood flow is much more severe. Skin may change color, and your hands may become painful. And it may happen with even mild cold exposure - just by taking something out of your freezer - or by stepping in a puddle on a cold day.
To cope with Raynaud's, you need good protection. Check out hunting and sporting goods stores for heavy-duty gloves and socks - maybe even with "warmers" built in. Remember that regular gloves are designed to reduce the amount of heat lost - not to provide heat on their own.
Also, be sure to protect your hands and feet from injuries. Cuts and other wounds may not heal as well due to reduced circulation. You are also more likely to get infections.
Should people with myositis have vaccinations?
There are probably no vaccinations that are contraindicated because of your disease alone. However, people who are taking immunosuppressants (such as methotrexate) may want to avoid "live" vaccines because their immune system may not be sufficiently strong to process the vaccine. ("Inactive" vaccines, such as the flu vaccine, are not live vaccines.) Check with your doctor on this issue.
Can vaccinations provoke the onset of inflammatory myopathies?
Doctors don't know whether any vaccines can actually provoke the onset of myositis. In fact, no one knows what sets off this illness. What makes certain people get it while others do not get it? Epidemiological research -- looking for common circumstances in those who get a disease -- can't tell us about "cause and effect" - only about factors associated with a disease. It is difficult to tease out whether an associated factor is actually the cause of the "effect."
With myositis, it is even more difficult to pinpoint when the disease actually began because of difficulty in recognizing and diagnosing this illness in a timely manner. Uncertainty about when myositis began obviously complicates the search for cause/effect progression.
About the Myositis Support Group of Hospital for Special Surgery
