Dermatomyositis

Definition

Dermatomyositis is a rare autoimmune disease belonging to the group of diseases called Idiopathic Inflammatory Myopathy (IMM), characterised by damage to the skin in addition to muscle damage.

Dermatomyositis is more common in women than in men.

Symptoms

Two main types of symptoms exist in dermatomyositis.

Muscle involvement is of varying severity. Symptoms associated with it include: difficulty climbing stairs, getting up from a chair, getting up from the floor, getting up from a squatting position, getting up after lying down. A person may also have trouble swallowing, as well as respiratory, heart, or digestive disorders.

Skin damage takes many forms. The signs of the attacks are located on the face, hands, nails, arms, forearms and neck. There are other types of skin involvement that are less characteristic of the disease.

The patient may also have fever, experience general fatigue, weight loss, or joint pain.

Causes and risk factors

The cause of the disease remains unknown. Some immunity factors, such as autoantibodies (antibodies made by the immune system targeting other organs), have nevertheless been linked to dermatomyositis.

Diagnosis

Dermatomyositis can affect children (Juvenile dermatomyositis) as well as adults. Juvenile dermatomyositis is rarer than dermatomyositis in adults.

The diagnosis is based on different criteria: skin damage and muscle weakness, increased presence of certain enzymes (according to the results of a blood test), abnormalities noticed during a microscopic examination of muscle cells (muscle biopsy),  MRI or electromyogram (EMG) abnormalities or the presence of antinuclear antibodies. 

Treatment

Different types of treatment can be used to reduce inflammation and thus eliminate the symptoms of the disease: corticosteroids, immunosuppressants, monoclonal antibody treatments (rituximab for example), immunoglobulins injected intravenously or even plasma exchange.

To treat skin damage, topical corticosteroids, tacrolimus ointment or hydroxychloroquine can be used.

Physiotherapy is an essential addition to drug treatments. During the period of inflammation, it allows passive and gentle joint mobilization. During the period of muscle recovery, when the inflammation subsides, rehabilitation helps recover functional capacities and prevent the development of muscle contractures.

Living with the disease

Symptoms may start to go away in about 3 months after the start of treatment.

Monthly follow-up visits are necessary during the first three months after the start of treatment, in order to closely follow the progression of the disease. If the condition improves, the appointments may be spaced out. Regular blood tests should be run to assess the evolution of certain biological parameters. Specific examinations of the organs affected by the disease must be carried out regularly (pulmonary, dermatological, rheumatology, neurological exams, for example).

Last updated: 12/4/21