Myositis is an inflammatory disease of muscle tissue. It can be triggered by a variety of causes, but is usually the result of autoimmune disease. Myositides occur mainly in association with other diseases, but on the whole represent a relatively rare clinical picture. Only 10 cases of illness per million inhabitants per year are recorded. The most common forms of disease are polymyositis, dermatomyositis and inclusion body myositis. Often, inflammation of the muscle tissue is associated with connective tissue inflammation.
Often, the cause of existing myositis can not be accurately named. In this case we speak of idiopathic myositis. Polymyositis and dermatomyositis, the two most common diseases in this area, are autoimmune-mediated disease processes known as autoimmune diseases. Its own immune system attacks the cells of the body with its defense cells and thus leads to their destruction. As a result, the affected tissue is inflamed.
In general systemic infections or inflammations, as well as in inflammatory processes in connective tissue, the muscles can be involved. If the myositis is triggered from the outside, this is done by bacteria, viruses or parasites. Particularly predestined for the formation of myositis are, for example, a disease of leprosy, gonorrhea (lues) and tetanus or parasitic infestation with schistosomes and Trichinella, both of which are worms. Overall, however, the mentioned infections occur less frequently in European latitudes. Bornholm disease, on the other hand, can also occur here, since the triggering Cocksacki B viruses can be found worldwide. Myositides can also be of hereditary origin, such as the Münchmeyer syndrome. But even this particular form of an inflammatory muscle disease is to be regarded as extremely rare because of their minor spread.
Depending on the clinical picture, the symptoms of myositis may be symmetrical or one-sided. However, it goes along with all forms of increasing loss of strength and muscle weakness and muscle pain. The intensity of the symptoms depends on the degree of inflammation. Without anti-inflammatory treatment, muscular degenerative processes can result, which manifest in visible muscle atrophy. Since all muscles of the entire body can be affected, localization in the pharyngeal and pharyngeal muscles may lead to dysphagia and hoarseness.
If, in principle, a degenerative course of the disease is at work, as in the case of Münchmeyer syndrome, the cells may undergo remodeling. In this rare case, lime salts are stored in the affected cells and lead to ossification of the muscles (myositis ossificans). Such cell calcification may also develop to a lesser extent in other forms of myositis. Basically, inflammatory processes mean stress on the cells of the affected tissue. Due to the constant decay and buildup of the cells, metaplasia, that is to say transformations of the cell structure, can occur. These can eventually lead to a degeneration of the tissue - a malignant tumor.
The diagnosis of myositis usually presents itself as complicated because it is difficult to differentiate between different clinical pictures. Guidelines should be the clinical symptoms as these may give an indication of the nature and localization of the inflammation. However, the majority of myositides is a creeping disease, which is noticed late. This increases the risk of developing lasting consequential damage. Basically, the examining doctor has three diagnostic instruments that can be used: a laboratory examination, an electromyography (EMG) and a muscle biopsy (invasive procedure in which muscle tissue is taken.
Laboratory Examination: When examining the laboratory parameters in the patient's blood, attention is primarily paid to enzymes that frequently occur in muscle cells and are released when the cells are damaged. The most important enzyme is the creatine kinase (CK). In addition, other parameters such as the activity of lactate dehydrogenase, aldolase and aspartate aminotransferase in the blood are measured. General signs of inflammation such as increased C-reactive protein, increased leukocyte count, or prolonged ESR are also detected, but only evidence of inflammation. The amount of myoglobin, a specific protein of skeletal muscle, can be additionally determined and included in the diagnosis. The value says nothing about the localization of the injury, but only the muscle cells are lost. If there is a suspicion of infestation with pathogens, it is possible to detect antibodies formed by the body against the pathogen and thus to indicate an existing infection or by PCR (polymerase chain reaction) to duplicate the DNA of the pathogen and represent so that computer-controlled accurate identification is possible. Myositis-specific antibodies, which are formed as part of the disease in some patients, in most cases have no conclusive validity, as these are also in other diseases, such as inflammation of the alveoli (alveolitis) or arthritis (joint inflammation) are formed.
Electromyography (EMG): In EMG, two smallest needles are inserted into the muscle to be examined. The needles conduct electrical current and measure voltage changes in muscle tissue. The changes are recorded and evaluated at rest and during tension. Most patients with myositis show conspicuous patterns, but these are not automatically proof of the disease. Nevertheless, EMG represents a straightforward examination, which can lead to the indication for further diagnostics. In addition, an electroneurography can be performed, in which the nerve conduction velocity and the muscle reaction time is measured. Here, a nerve is excited by means of applied electrodes and paid attention to the resulting muscle twitch. Accompanying nerve damage or other diseases can be proved or excluded, which plays a key role in differential diagnosis (other diseases with consistent symptoms).
Muscle biopsy: Since muscle biopsy is an invasive procedure, the location of the procedure should be planned. This is usually done by an MRI (Magnetic Resonance Imaging). The biopsy should not be performed at a site where an EMG has previously taken place. The punctures through the needles lead to local cell death, which can no longer be distinguished from a myositis with hindsight. Once the right biopsy site has been found, biopsy specimens (biopsied tissue) can show general features of myositis by light microscopy, but tissue changes specific to different forms can also be observed. Characteristic features include both muscle fiber subsidence (dead / necrotic muscle fibers), as well as regenerated sections of muscle fibers and typical signs of inflammation - tissue infiltration (immigration) by inflammatory cells. With low disease activity, the diagnosis can be complicated by missing or difficult to find cell signs.
Since myositis is one of the inflammatory skeletal muscle diseases, which may have an autoimmune reaction, ie a falsely reaction of the body's defense system against the body's own structures, as the cause, it is therefore possible to detect certain antibodies in the blood of the affected patients.
These antibodies are components of the immune system, are formed by the so-called B-lymphocytes and are directed in the context of an autoimmune disease against - here in the case of a myositis - structures of skeletal culture, called antigens. Myositis distinguishes between myositis-specific and myositis-associated antibodies.
The former are found in about 15-50% of the patients in the blood serum and can be measured by a blood sample.
Antibodies to tRNA synthetases, such as, for example, Jo-1 antibodies, PL-7 antibodies, EJ antibodies or KS antibodies, belong to the myositis-specific antibodies. The myositis-associated antibodies include anti-Mi-2, anti-SRP and anti-Pm-Scl.
Polymyositis is the rarest form of common inflammatory muscle diseases. It occurs more frequently in two stages of the patient's life: from 5 to 14 years of age in adolescents and 45 to 65 years in adulthood. On average, twice as many women as men are affected by polymyositis. Clinically, the disease is characterized by mostly symmetrical muscle weakness in the area of the shoulder-neck-belt and the hip - ie the muscles close to the trunk. The weaknesses develop relatively fast compared to inclusion body myositis, over weeks to months. The lack of muscle power can lead to painful poor posture, by scarring of inflamed muscle sections to malalignment of joints. The tissue sample taken by biopsy has inflammatory cells that migrate between the muscle fibers. The disease process of polymyositis is not fully understood yet. However, it is believed to be an autoimmune disease. In contrast to dermatomyositis, however, it is mediated by a direct cellular response of the body and not by corresponding proteins.
Overall, dermatomyositis occurs more often than polymyositis, ignoring age. Age-specific accumulation is observable as in polymyositis. Women are more affected than men. Among the symptoms that affect skeletal muscle, dermatomyositis shows changes in the skin. It lilac rashes (erythema) in light-exposed areas of the body, which is why the name has developed Lilac disease. The skin becomes flaky, especially in areas over joints such as the fingers, elbows and knees. The rash may cause swelling of the upper eyelids, giving the patient a whiny look on his face. This can be intensified by scarring of the flaky skin.
The changes described can be more or less pronounced. If a muscle biopsy is performed, the perivascular (perivascular) inflammatory cells can be detected in the preparation. Also between the individual muscle fiber bundles (interfaszicular) accumulate corresponding cells. Peripheral muscle fibers become narrower relative to the remainder of the bundle. This is called perifascicular atrophy. The pathomechanism (disease process) is based on an autoimmune reaction directed against the capillaries (smallest vessels) in the muscles. These are attacked and damaged by the body's own inflammatory proteins (eg immunoglobulins). Consequently, the muscle fibers can no longer be supplied and die.
It comes to local necrosis (cell death) and vascular thrombosis (closure of a vessel by a blood clot / thrombus) - the muscle fiber bundles decrease in strength and eventually atrophied. In more than a quarter of the diseases of dermatomyositis, a malignant tumor is the cause of its development. Again, the body forms substances that are directed both against the tumor, and against healthy body tissue.
Inclusion body myositis is a chronic progressive (inflammatory) degenerative disease. The causal process in the body has not yet been clarified, but an interaction of inflammatory and degenerative factors is suspected. It affects men in 75 percent of the cases and occurs mainly after the age of 50. The course is rather insidious - it sometimes takes months to years until the first clinical symptoms occur. Patients first notice problems climbing stairs or getting up from a sitting position. Difficulties to hold a firm grip or even to execute it are also characteristic. The symptoms are caused by the progressive weakness of the forearm and thigh muscles. Sixty percent of sufferers report difficulty swallowing as they also need muscle that may be affected by the inflammation. The preparation made from a biopsy is similar in nature to polymyositis. One recognizes immigrated inflammatory cells and submerged fiber strands. In addition, inclusions, so-called "vacuoles" (in English: surrounded vacuoles, vacuole = cell vesicles) can be found in the tissue. The inclusion bodies contain various protein structures, α-amyloid and tau proteins. These compounds are also found in other degenerative diseases, such as Alzheimer's disease.
Münchmeyer Syndrome (Fibrodysplasia ossificans progressiva): Due to an inherited genetic defect that influences the development of skeletal muscle, so-called Münchmeyer syndrome occurs. It comes over years for the storage of calcium salts in muscle cells and consequently to the ossification of the muscles. Beginning in the neck, the disease progresses from top to bottom, over the shoulder region into the arms and torso. Since there is currently no proven way to therapy, let alone for healing, it comes in the final stages of the disease to the ossification of the respiratory muscles and thus more difficult breathing, up to suffocation. Since most patients remain childless and do not pass on the genes, the spread of Münchmeyer syndrome is very limited.
Bornholm epidemic (epidemic pleurodynia) epidemic pleurodynia is an inflammatory disease of the pleura, the abdominal and abdominal muscles. It is caused by infection with Cocksackie B viruses, from the enterovirus family. Symptoms include pain during breathing, mild fever and a reddened throat. The pain is caused by the involvement of the intercostal muscles, the muscles between the ribs, which is part of the respiratory muscles. Bornholm disease can be transmitted from person to person and, by default, is treated with analgesics according to the symptoms.
Myositis on the eye, also called ocular myositis, is an idiopathic ( that is, without a known cause occurring ) inflammation of the eye muscles.
It is one of the third most common diseases of the orbit and comes right after the eye involvement in the thyroid hyperfunction and in lymphoproliferative disorders.
The exact cause of myositis in the eye has not yet been fully elucidated, an autoimmune reaction, that is, a false reaction of the body's own defense system, is falsely recognized as falsely recognizing and combating certain cellular structures.
The most frequently affected are women in adulthood ( mean age of onset: 34 years ), with symptoms more often one-sided (only one eye affected) than bilateral:
The eye muscle most commonly affected is the straight medial muscle ( rectus medialis ), which usually moves the eyeball toward the nose. The ocular myositis is usually diagnosed on CT, it is treated by the use of glucocorticoids (cortisone), so that the inflammation usually fades away without consequences within several days.
The term " myositis ossificans " includes two medical conditions.
On the one hand, this refers to heterotropic ossification, which is a disease in which there is ossification at various points of the body either spontaneously or after trauma and after surgery.
On the other hand, the term " myositis ossificans " also includes a rare hereditary disease - the myositis ossificans progressiva. This is a congenital genetic defect that causes the skeletal body of the body to be relocated progressively into bone tissue. Only about 600 people worldwide are affected by this hereditary disease. The cause of the bony reconstruction is the inability to repair defective skeletal muscles after common trauma or trauma with healthy muscle tissue or scar tissue - bone tissue is used instead.
Over time, it comes to an increasing inoperability of the muscular system, life-threatening, the disease is when organs are affected by the ossification (eg respiratory dysfunction due to increasing ossification of the intercostal muscles and thus the chest ).
The treatment of dermatomyositis and polymyositis corresponds to the mostly used therapy of autoimmune diseases. Cortisone is administered, which partially inhibits the immune system and causes flattening of the inflammation, so that the tissue can recover. This relatively high doses are used, which are gradually reduced over a longer period. The effect begins, depending on the patient, for days to weeks, in a delayed case after 1-2 months. Longer cortisone delivery, however, is associated with a variety of side effects, such as muscle loss, osteoporosis or mental changes. If the therapy does not have the desired effect or if the dosage has to be reduced due to side effects, cytostatic drugs such as methotrexate can also be used, which also have a fixed place in the tumor treatment and additionally compress the immune system. The administration of high-dose immunoglobulins may be helpful in polymyositis and dermatomyositis, but is particularly controversial in the treatment of inclusion body myositis. In addition to the medical therapy, physiotherapy and occupational therapy can be used to maintain freedom of movement and to prevent muscle contractions (contractions). In severe muscle weakness, the use of walking aids or wheelchairs, paralysis, muscle hardening or injury may require further treatment.
Regular therapy can achieve complete healing in half of the patients with polymyositis. Otherwise, a standstill with more or less permanent muscle weaknesses can be achieved. However, in 20% of cases there is the possibility that, despite extensive therapy, no success can be recorded.
The dermatomyositis can also be cured by appropriate therapy or at least limited. The treatment of the often triggering tumor diseases can cause a lasting improvement of the symptoms or a healing of the consequential illness.
Since the drug therapy of an inclusion body myositis is not promising, a constant range of exercise must be sought through physiotherapy and independent exercises. Even light strength exercises and muscle endurance training can counteract the symptoms. In the case of disturbing impairment of the pharyngeal muscles, the visit to a speech therapist can be relieved to improve the swallowing symptoms. Helpful movements or postures are practiced, which facilitate the swallowing process.