Overview
Myositis is an inflammatory disease of muscle tissue. It can be triggered by a variety of causes, but is usually the result of an autoimmune disease. Myositides mainly occur in association with other diseases, but overall they represent a relatively rare clinical picture.
Only 10 cases of myositis are recorded among one million inhabitants per year. The most common forms of the disease are polymyositis, dermatomyositis and inclusion body myositis. Inflammation of muscle tissue is often associated with inflammation of connective tissue.
Cause
Often the cause of an existing myositis cannot be named exactly. In this case one speaks of an idiopathic myositis. Polymyositis and dermatomyositis, the two most common clinical pictures in this area, are autoimmune mediated disease processes, so-called autoimmune diseases.
Here, the body’s own immune system with its defense cells attacks the body’s own cells and thus leads to their destruction. As a result, the affected tissue becomes inflamed. In the case of general systemic infections or inflammations, as well as inflammatory processes in the connective tissue, the muscles can be involved.
If the myositis is triggered externally, it is caused by bacteria, viruses or parasites. Particularly predestined for the development of myositis are, for example, a disease of leprosy, gonorrhea (lues) and tetanus or parasitic infestation with schistosomes and trichinella, which are both worms. Overall, however, the above-mentioned infections occur less frequently in European latitudes.
Bornholm disease, on the other hand, can also occur here, since the Cocksacki-B viruses that cause the disease are found worldwide. Myositides can also be of hereditary origin, like Münchmeyer syndrome. But even this special form of an inflammatory muscle disease is extremely rare due to its slight spread.
Symptoms
Depending on the clinical picture, the symptoms of myositis can be symmetrical or one-sided. However, in all forms it is accompanied by increasing loss of strength and muscle weakness as well as muscle pain. The intensity of the symptoms depends on the degree of inflammation.
Without anti-inflammatory treatment, muscle degenerative processes may occur, which manifest themselves as visible muscle atrophy. Since all muscles of the entire body can be affected, localization in the throat and pharyngeal muscles can lead to swallowing disorders and hoarseness. If a degenerative course of the disease is underlying, as in the Münchmeyer syndrome, the cells can be transformed.
In this rare case, calcium salts are stored in the affected cells and lead to ossification of the muscles (myositis ossificans). Such cell calcification can also develop to a lesser extent in other forms of myositis. Basically, inflammatory processes mean stress for the cells of the affected tissue. The constant breakdown and build-up of the cells can lead to metaplasia, i.e. changes in the cell structure. These can ultimately lead to degeneration of the tissue – a malignant tumor.
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