Myopathy is a group of diseases that affect the muscles. Myopathy may have a genetic origin, affecting the production of proteins involved in muscle formation. Myopathy can take many forms.
One of the forms of myopathy is muscular dystrophy , characterized by progressive degeneration of muscle cells. There are different types of muscular dystrophies, the most common being Duchenne muscular dystrophy .
There are also myopathies caused by infection, injury or autoimmune disease. These inflammatory myopathies are rare diseases that cause pain and muscle weakness and can progress to decreased muscle mass and severe disability. The most common are polymyositis , dermatomyositis and inclusion myositis . These three diseases affect the skeletal muscles ( muscles of voluntary movements).
Other myopathies may be caused by metabolic disorders (glycogenosis, enzyme deficiency) or endocrine disorders (dysfunction of the thyroid gland or the adrenal gland) or be caused by the use of certain drugs (amphetamines, heroin) or drugs ( antipsychotics, statins, some antidepressants, and colchicine).
|In this file, only inflammatory myopathies, including polymyolitis, dermatomyositis and inclusion myositis, will be discussed.|
Causes of Myopathy
The exact cause of inflammatory myopathies is unknown. According to research, they have an autoimmune component, which occurs when the immune system, which normally protects the body against infections, disrupts and attacks the cells of the body, then destroys them.
Inflammatory myopathies are not considered genetic diseases, but there is a hereditary component that predisposes some people to the development of autoimmune diseases.
Inflammatory myositis is a rare disease. The prevalence of dermatomyositis and polymyositis is estimated at about 6-7 cases per 100,000 population. The prevalence of inclusion-related myositis would be 5 to 9 cases per 1,000,000 people.
Inflammation of the muscles caused by dermatomyositis can lead to:
- Difficulty swallowing. When the esophagus muscles are affected, difficulty swallowing (dysphagia) can cause weight loss and malnutrition.
- Aspiration pneumonia. Difficulty swallowing may contribute to the aspiration of food or fluids, including saliva, into the lungs, which can lead to pneumonia.
- Difficulty breathing. When myopathy affects the chest muscles, those affected may have trouble breathing or shortness of breath.
- Gastrointestinal problems , such as the appearance of ulcers or intestinal perforations causing bleeding.
- Cutaneous complications , such as calcium deposits in muscles, skin or tissues, called calcinosis, as the disease progresses.
- A greater risk of infection especially to the respiratory and digestive system.
People with dermatomyositis are also at higher risk of developing:
- Raynaud’s disease.
- Other connective tissue diseases, such as lupus, rheumatoid arthritis, scleroderma, and Sjogren’s syndrome.
- Cardiovascular diseases, eg myocarditis, heart failure or cardiac arrhythmia
- Pulmonary diseases, for example interstitial lung disease.
- Cancer, especially cervical cancer , lung cancer, pancreatic cancer, breast cancer, ovarian cancer and gastrointestinal tract cancer.
Symptoms of Myopathy
- Progressive muscle weakness that affects several muscles, and in the first place, the muscles surrounding the hips and the shoulder girdle.
- Difficulty walking, getting up from a seat or getting out of bed.
- As the disease progresses, a left gait and frequent falls.
- Excessive fatigue
- Difficulty swallowing or breathing.
- Painful or sensitive muscles.
Particular signs of a polymyositis:
- Muscular weakness appearing mainly in the arms, shoulders and thighs, both sides at a time.
- The appearance of weakness of the pharyngeal muscles responsible for swallowing (swallowing).
Particular signs of a dermatomyositis:
Dermatomyositis occurs in children between 5 and 15 years of age or in adults from the late 40s to early 60s. These main symptoms are:
- A rash that is purple or dark red, most commonly on the face, eyelids, near nails or knuckles, elbows, knees, chest, or back.
- Progressive weakness of the muscles near the trunk, such as hips, thighs, shoulders and neck. This weakness is symmetrical, affecting both sides of the body.
These symptoms are sometimes accompanied by:
- Difficulty swallowing.
- Muscle pain
- Fatigue, fever and weight loss.
- In children, calcium deposits under the skin (calcinosis).
Particular signs of myositis with inclusions:
- Progressive muscle weakness first affecting the wrists, fingers and hips. For example, sufferers have difficulty grasping a heavy bag or suitcase and stumble easily). Muscle weakness is insidious and the average duration of symptoms is six years before diagnosis.
- Muscle involvement is usually symmetrical, that is, weakness is similar on both sides of the body. However, it can also be asymmetrical.
- Weakness of the muscles responsible for swallowing (in one third of patients).
People at risk for Myopathy
- Polymyositis and dermatomyositis are more common in women (2 women for 1 man) and usually begin between 40 and 60 years of age, but can occur at any age.
- Dermatomyositis is more common in children than in adults.
- Inclusion myositis occurs more often in men than in women, generally affecting adults 50 years and older.
|Can I prevent myopathy?|
|It is not possible to prevent the appearance of inflammatory myopathies.
Measures to prevent aggravation
In people with dermatomyositis, the areas affected by rashes are more sensitive to the sun. As a precaution, wear protective clothing or sunscreen with a high level of protection when going outdoors.
Medical treatment of myopathy
There is no cure for inflammatory myopathy. However, some medications can help to reduce the symptoms.
- Corticosteroids . Polymyositis and dermatomyositis are usually treated with high doses of corticosteroids (prednisone).
- Immunosuppressants . If corticosteroids are poorly tolerated, immunosuppressive drugs such as azathioprine or methotrexate may be used to reduce inflammation. In certain circumstances, other immunosuppressants may be indicated, such as tacrolimus, cyclophosphamide and cyclosporine.
- Immunoglobulins . Intravenous infusions of antibodies from donors (intravenous immunoglobulin or IVIG) are sometimes used. The effects are beneficial, but of short duration and it are often necessary to repeat the infusions at 6 to 8 weeks.
Symptoms of inclusion myositis respond less well to this type of medication. Some results have been promising with the combination of corticosteroids-methotrexate or corticosteroids-intravenous immunoglobulin.
- Ointment with corticosteroids . People with dermatomyositis treat rashes with a topical ointment.
- Surgery . Surgery is sometimes necessary to remove calcium deposits (calcinosis) that cause pain and recurrent infections.
In addition to medication, many treatments can both relieve symptoms and slow the progression of the disease:
- The therapy can delay the loss of muscle function and to conserve energy.
- The use of orthopedic devices such as knee, leg and back splints helps to maintain muscle flexibility.
- The occupational therapy teaches people to use wheelchairs, as well as techniques allowing them to perform various daily tasks.
- The speech therapy is indicated for people with swallowing disorders.
- The surgery is sometimes considered to relieve advanced tendon problems.
Many clinical, fundamental and therapeutic protocols are in progress to treat inflammatory myopathies. They include the use of drugs, such as rituximab, etanercept, infliximab or a combination of these drugs.