Dermatomyositis is an inflammatory muscle disorder belonging to the group of inflammatory myopathies, which also includes polymyositis, myositis associated with scleroderma and lupus and inclusion myositis. Dermatomyositis is said to affect between 1 in 200,000 people worldwide. According to Orphanet, women are twice as likely to develop it as men. It can occur at any age, but it occurs especially in children between 5 and 14 years old: in this case, we talk about juvenile dermatomyositis. In adults, it frequently appears between 50 and 60 years of age.
What is dermatomyositis?
Dermatomyositis is characterized by inflammatory damage to certain areas of the skin and certain muscles. This disease is not related to an infection or a gene abnormality. It is therefore neither contagious nor transmissible to her children. Dermatomyositis is a weakness or disability in the muscles and is accompanied by muscle pain, especially in the thighs, arms, shoulders, buttocks and neck. Another manifestation: rashes and redness on the face. This condition is severe and its complications are numerous. Dermatomyositis usually develops slowly over several weeks or months. However, in some cases, its evolution can be faster and it sometimes becomes disabling.
Dermatomyositis: what are the causes?
The Orphanet indicates on its site that the precise origins of dermatomyositis are currently unknown. Dermatomyositis is an autoimmune disease. "For some reason, the body's immune system turns against its own muscles with an autoimmune reaction", explains the Cochrane organization on its website.
Normally, the immune system produces antibodies that attack and neutralize so-called foreign elements, such as viruses or bacteria. In the case of dermatomyositis, the immune system reacts against certain cells in its own organism. This phenomenon can lead to the destruction of its own antibodies.
The Orphanet specifies that at least some of the people with dermatomyositis produce autoantibodies directed against certain muscle and skin cells. "It is not yet known why the immune system is being upset, but several factors (eg, genetic, environmental, or, rarely, taking a drug) are likely to be involved. , autoimmune reactions may not be the only cause of the onset and course of the disease, and other mechanisms are involved, including damage to the skin. nor why dermatomyositis, like most autoimmune diseases, affects women more often than men ", he specifies.
What are the symptoms of dermatomyositis?
Dermatomyositis first manifests as skin symptoms. Muscle damage occurs several weeks or months after the first signs. Skin signs appear as red patches on the face, neck, shoulders or hands and are associated with mild edema in the area. They appear suddenly, sometimes after exposure to the sun, and do not itch.
These plaques are sometimes located at the level of the upper eyelids and take on a purplish hue or give a "glasses-like" appearance. This characteristic can also occur at the elbows and knees. When the patches are localized on the bust, the skin can become thinner, wrinkled and dark and light spots may appear.
According to Orphanet, 30% of people with dermatomyositis have small, hard, red, purplish lesions on their fingers. The part around the nails can also be affected. In this case, it is red and painful, especially when the patient exerts pressure. 10 to 15% of people with dermatomyositis also suffer from Raynaud's syndrome. This disruption of blood flow to the extremities causes episodes of paleness and blue stain on the fingers or toes. Scalp damage, similar to that seen in psoriasis, can also occur when you have dermatomyositis.
Small "balls" hard to the touch and sometimes visible under the skin may occur in one in three children. It is a calcinosis, in other words lime deposits. These calcifications can also form in the muscles and around the joints and can sometimes hinder movement.
In most cases, dermatomyositis causes muscle weakness. Its importance varies depending on the individual. Some patients may be uncomfortable and others may find it difficult to walk. The muscles can become tender and swollen when the disease progresses or if it is a severe case.
The pathology is also accompanied by:
Dermatomyositis: how to diagnose it?
The presence of red plaques and muscle damage allow healthcare professionals to suspect dermatomyositis. To assess muscle strength, the practitioner can ask the patient to perform muscle testing. This involves observing how the person with the disease is able to move their limbs and a score is assigned to each muscle. The doctor can also assess his ability to maintain and stay in certain positions. Muscle strength can also be assessed by a muscle MRI, an electromyogram, a muscle biopsy or blood tests.
How to treat dermatomyositis?
The treatments indicated to cure dermatomyositis consist in reducing the muscular deficit by fighting against inflammation and the production of autoantibodies. Initially, the doctor generally prescribes corticosteroid therapy. This treatment contributes to the disappearance of muscle manifestations.
Another possibility: immunomodulators or immunosuppressants, which act on the immune system and limit the production of autoantibodies. They can be administered in addition to corticosteroid therapy to reduce the amounts of corticosteroids and its side effects. Hydrochloroquine is sometimes necessary to heal skin lesions. Healthcare professionals also recommend that patients use sunscreen creams frequently to reduce skin problems.
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