These are inflammations of skeletal muscles, which are of unknown origin. Immune mechanisms are involved, where the immune system attacks organs for unknown reasons. They are not considered to be hereditary.
They can be distinguished in:
It affects all ages and sexes, but is more common in women. It is the most easily recognizable myositis due to severe skin rash, which usually precedes muscle weakness. This rash is uneven, dark red or purple and is seen in eyelids, cheekbones, nose, back, chest, elbows, knees and joints. Some patients show hardening under their skin (asbestosis). Muscular weakness and rash are due to inflammation that occurs in the vessels under the skin and muscles (vasculitis).
If there is only rash, then the condition is characterized as amyotrophic dermatomyositis. The weakness begins in the muscles of the torso such as of the throat, hip, back, shoulders. Some patients may experience muscle pain. It manifests with generalized fatigue and weakness in movements such as lifting the body from the sitting position. In addition, the skin is scaly, hard or dry. There is dysphagia, dysphonia and swelling around the nail area, gastroesophageal reflux, respiratory problems, cardiomyopathies, arrhythmias and malignancies. Diagnosis can be performed by a dermatologist and neurologist, blood tests for muscle enzyme assays such as aldolase, antibodies, respiratory tests, esophagus, electrocardiogram, and colonoscopy, Pap test and tumor markers for malignancy. In addition, electromyography, magnetic resonance imaging, chest X-ray, barium test and skin and muscle biopsies are performed.
2. Juvenile dermatomyositis
It occurs in children younger than 18 years of age, with rashes, uneven on the eyelids or cheekbones, and at the same time or immediately after the onset of rash, muscle weakness may occur in muscles near torso, causing problems in lifting and climbing due to vasculitis. In addition, dysphonia, dysphagia is present, in 50% of patients there is muscle pain, asbestosis of the skin, muscular contractures and stomach problems and pain.
3. Inclusion-Body Myositis - IBM
It is more common in men and usually occurs after the age of 50 years. A small number of patients inherit the disease, but most are sporadic cases, as long as there is no specific genetic cause. It evolves gradually over months or years, while there is no cure, although gene therapy efforts are being made. Muscle weakness occurs in quadriceps and muscles under the knee, leading to frequent falls and failure to change stair position and climb, muscle weakness in the forearms and finger muscles leading to inability to grasp, neck muscles leading to dysphagia and often choking, as well as muscle pain.
It is more common in people over 20 years and especially in women. There is a gradual occurrence of muscle weakness, affecting muscles near the torso, but it can also affect muscles of the hands and fingers. It usually coexists with other autoimmune diseases and is difficult to be distinguished from IBM. In addition, there is dysphagia, falls and inability to lift, chronic dry cough, tingling sensation and thickening of hand skin.
5. Orbital myositis (or idiopathic myositis)
It is particularly rare and refers to orbital inflammation of the external eye muscles, which are responsible for the movement of the eyes. It occurs mainly in young women or middle-aged women. The cause is unknown, but it is believed that autoimmune processes are involved since there is association with various autoimmune diseases, such as Crohn's disease, systemic lupus erythematosus, rheumatoid arthritis, diabetes mellitus, myasthenia, and ankylosing spondylitis. It is presented with gurgling eyes, ptosis of the eyelids, diplopia, redness and eye swelling, pain in the movement of the eyes.
Information about clinical trials conducted globally: https://www.centerwatch.com/clinical-trials/listings/condition/263/dermatomyositis-connective-tissue-disease/
Muscular Dystrophy Association