What is it?
Dermatomyositis is a chronic disease that affects the skin and muscles. It is an autoimmune disease whose origin is still unknown, classified in the group of idiopathic inflammatory myopathies, alongside for example polymyositis. The pathology evolves for years with a good prognosis, in the absence of serious complications, but can hinder the motor skills of the patient. It is estimated that 1 in 50,000 to 1 in 10,000 people live with dermatomyositis (its prevalence) and that the number of new annual cases is 1 to 10 per million people (its incidence).
Symptoms of Dermatomyositis
The symptoms of dermatomyositis are similar or similar to those associated with other inflammatory myopathies: skin lesions, muscle pain and weakness. But several elements distinguish dermatomyositis from other inflammatory myopathies:
- The slightly swollen red and purple patches on the face, neck and shoulders are usually the first clinical manifestations. The possible involvement in the eyelids, in the form of glasses, is characteristic.
- The muscles are touched symmetrically, starting from the trunk (abdominal, neck, trapezius …) before reaching, in some cases, the arms and legs.
- The high probability of being associated with cancer. This cancer usually occurs in the months or years following the disease, but sometimes as soon as the first symptoms appear (it also happens that it precedes them shortly). It is most often breast or ovarian cancer for women and lung, prostate and testicles for men. The sources do not all agree on the risk for people with dermatomyositis to develop cancer (10-15% for some, one third for others). Fortunately, this does not concern the juvenile form of the disease.
An MRI and a muscle biopsy will confirm or invalidate the diagnosis.
The origins of the disease
Remember that dermatomyositis is a disease belonging to the group of idiopathic inflammatory myopathies. The adjective “idiopathic” meaning that their origin is not known. So far, neither the cause nor the precise mechanism of the disease is known. It is likely to result from a combination of genetic and environmental factors.
However, we know that it is an autoimmune disease that is to say, causing a disruption of immune defenses, auto-antibodies turning against the body, in this case against certain cells of the body. Muscles and skin. It should be noted, however, that not all people with dermatomyositis produce these autoantibodies. Drugs could also be triggers, as well as viruses.
Risk factors for Dermatomyositis
Women are more often affected by dermatomyositis than men, about twice as much. This is often the case with autoimmune diseases, without knowing the reason. The disease can occur at any age, but it is found that it appears preferentially between 50 and 60 years. With regard to juvenile dermatomyositis, it is usually between 5 and 14 years old that it appears. It should be emphasized that this disease is neither contagious nor hereditary.
Prevention and treatment of Dermatomyositis
In the absence of being able to act on the (unknown) causes of the disease, dermatomyositis treatments aim at reducing / eliminating inflammation by administering corticosteroids (corticosteroids), as well as combating the production of autoantibodies in the body. Immunomodulatory or immunosuppressive drugs.
These treatments help to limit pain and muscle damage, but complications can occur in case of cancer and various disorders (heart, lung …). Juvenile dermatomyositis can cause severe digestive disorders in children.
Patients must protect their skin from the sun’s UV rays, which would aggravate the skin lesions, by means of covering clothing and / or strong sun protection. As soon as the diagnosis is made, the patient must undergo regular tests for cancers associated with the disease.