What are inflammatory myopathies (Myositis)?
Myopathy is the medical term for muscle disease. Some muscle diseases occur when the body’s immune system attacks muscles. The result is misdirected inflammation, hence the name inflammatory myopathies or myositis. The inflammation damages muscle tissue and makes muscles weak.
People with inflammatory myopathies may have these features:
- Weakness in the large muscles around the neck, shoulders and hips
- Trouble climbing stairs, getting up from a seat, or reaching for objects overhead
- Little, if any, pain in the muscles
- Choking while eating or aspiration of food into the lungs
- Shortness of breath and cough
The inflammatory myopathies include polymyositis and dermatomyositis. Muscle inflammation and weakness occur in both conditions while patients with dermatomyositis also have a rash. This rash most often appears as purple or red spots on the upper eyelids or as scaly, red bumps over the knuckles, elbows or knees. Children with the disease also may have white calcium deposits in the skin called calcinosis.
Sometimes patients can have the rash with no sign of muscle disease. Doctors call this form of the disease amyopathic dermatomyositis.
People with myositis may also have lung inflammation that causes cough and shortness of breath. Children with the disease may have an inflammation of the blood vessels (vasculitis) that can result in skin lesions.
Who gets Myositis?
Inflammatory myopathies are rare. Polymyositis and dermatomyositis occur in about one person per 100,000.
All ages can get these diseases. The peak time to get them, though, is ages 5 to 10 in children, and 40 to 50 in adults. Women get inflammatory myopathies about twice as often as men. These diseases affect all ethnic groups. No one can predict who will get inflammatory myopathy.
What causes Myositis?
There are many causes of muscle disease. They include infection, muscle injury due to medicine, inherited diseases that affect muscle function, disorders of electrolyte levels, and thyroid disease.
We do not know what causes inflammatory myopathies. It is postulated that something goes wrong in the immune system that leads to inflammation. This damages muscle cells or the blood vessels present in the muscle.
Fingers of a person with dermatomyositis show red bumps on the knuckles (referred to as Gottron’s papules), redness around the nails and thick, ragged cuticles.
How is myositis diagnosed?
A doctor suspects myopathy when patients complain of trouble doing tasks that require muscle strength, or when they get certain rashes or breathing problems.
Most people with myopathy have little or no pain in their muscles. This differs from other health problems. Examples are other forms of muscle disease, joint pain due to arthritis
and nerve problems that cause numbness or tingling in the hands and feet. Many patients with other illnesses think they feel weak. In fact, they are tired, short of breath or depressed, rather than having true muscle weakness.
A doctor will do a muscle strength exam to find if true muscle weakness is present. The following test may then be needed:
- A blood test to measure the level of various muscle enzymes
- An electromyogram — often referred to as an EMG— to gauge electrical activity in muscle
- A biopsy of a weak muscle (a small piece of muscle tissue) is removed for testing
- Magnetic resonance imaging — more often called MRI — to try to show abnormal muscle
Some patients may have a blood test for myositis-specific antibodies (immune proteins). This test helps detect myopathy. It also gives some information about prognosis (how serious the disease is and how it will progress).
How is Myositis treated?
Doctors most often treat these diseases with immunosuppressive medications.
Corticosteroids: Often, the first treatment is an oral (by mouth) corticosteroid, such as prednisone, at a high dose. This reduces inflammation. Blood muscle enzyme levels tend to return to normal about 4−6 weeks after treatment starts. Most patients regain muscle strength in 2−3 months.
Combination treatment: Your doctor likely will add another drug to your treatment plan: Methotrexate or Azathioprine. This gives better long-range control of the disease and helps avoid long-term side effects of corticosteroids. These side effects include weight gain and redistribution of body fat, thinning of the skin, osteoporosis and cataracts. Even muscle weakness can be a side effect of treatment with corticosteroids (steroid induced myopathy).
Because patients taking prednisone are at risk for osteoporosis, they should receive proper treatment to prevent it.
Immune treatments: Patients whose disease is severe or who do not respond to standard treatment have other options. They include intravenous immunoglobulin — sometimes referred to as IVIg — or medicines that suppress the immune system. These immunosuppressive drugs include Cyclosporine, Tacrolimus, Mycophenolate mofetil and Rituximab.
Physical therapy: Physical therapy and exercise are important in the treatment of muscle disease. Very weak patients who do not walk should receive a range of motion exercises. These exercises prevent joint contractures (deformity of the joint). Patients with medium weakness should start an exercise program to strengthen their muscles. The goal is to slowly increase in intensity as the patient regains strength. Mildly weak patients should take part in their normal activities.
Physical therapy can help patients with muscle disease go on leading active lives.
Broader health impacts of Myositis
In adults, dermatomyositis and to a lesser extent polymyositis may be related to an underlying cancer. Therefore all adult patients above 40 years of age with these disorders should receive appropriate testing to rule out cancer.
Living with Myositis
Myopathies are chronic (long-term) diseases. To help control your illness, it is important to practice good health measures. Eat a healthy, well-balanced diet, exercise and try to keep a healthy weight.
If you have a dermatomyositis rash, protect yourself from the sun. This is because the rash gets worse after sun exposure, for reasons that are not clear. Therefore, limit time outdoors, and put on sunscreen (SPF>30) when you go outside.
If you have trouble swallowing, eat soft or semisolid foods, or puree your solid foods. To prevent choking if you are bedbound, you should be seated up in bed to eat.
People with myopathy may look healthy and normal. It is important for employers, teachers and family members to understand the limits that muscle weakness causes in people with myopathy.