Polymyositis

Introduction to polymyositis Polymyositis is a systemic connective tissue disease characterized by inflammation, degeneration, and other changes in the muscle tissue (the skin is also often affected, ie, dermatomyositis), resulting in symmetrical muscle weakness and a certain degree of muscle atrophy, mainly in the limbs. muscle. The cause is unknown. May be caused by an autoimmune reaction. The disease is not uncommon, the incidence is lower than systemic lupus erythematosus and progressive systemic sclerosis, but higher than nodular polyarteritis. The ratio of male to female is 1:2. People of any age group can develop the disease, but the highest incidence rate is 40 to 60 years old, or 5 to 15 years old. Patient activity must be limited until the inflammation subsides. Adrenal cortex hormone is the drug of choice. For acute patients, prednisone is given at a dose of 40-60 mg/d or more. Continuous measurement of serum muscle enzyme activity is the best way to observe the effect. basic knowledge The proportion of illness: 0.02-0.05% Susceptible people: no special people Mode of infection: non-infectious Complications: cough, arrhythmia

Cause of polymyositis

The cause is unknown. Cell-mediated immune responses play an important role in muscle. The virus may also be involved in the pathogenesis: microRNA-like structures have been found in muscle cells, and tubular inclusion bodies resembling paramyxovirus nucleocapsids have been found in myocytes and endothelial cells of the skin and muscle wall using electron microscopy. . A related phenomenon of malignant tumors and dermatomyositis (much more polymyositis) suggests that tumors can cause myositis, which is the result of an immune response against a common antigen of muscles and tumors.

The disease is not uncommon, the incidence is lower than systemic lupus erythematosus and progressive systemic sclerosis, but higher than nodular polyarteritis. The ratio of male to female is 1:2. People of any age group can develop the disease, but the highest incidence rate is 40 to 60 years old, or 5 to 15 years old.

Pathology

Dermatological examinations were found to be non-specific, such as epidermal atrophy, basal cell liquefaction, degeneration, vasodilation, and lymphocytic infiltration. The affected muscle tissue lesions vary widely. Common changes include necrosis, phagocytosis, muscle fiber regeneration, muscle cell basophilic, nuclear hypertrophy and vacuolization, nucleolar protrusion, muscle fiber atrophy and degeneration, especially around the muscle bundle of patients with dermatomyositis; , vacuole formation; muscle fiber size variation; lymphocyte infiltration (particularly significant around the blood vessels); endometrial and later connective tissue in the fascia. Inclusion of body myositis-inflammatory myopathy is another subtype. Muscle biopsy shows that muscle fiber necrosis and perivascular inflammatory cell infiltration are not obvious. Common muscle fiber hypertrophy contains basophilic granules in the surrounding vacuoles. Under the electron microscope, the inclusion body can be most specifically identified. In children (derived dermatomyositis is more common), ulcers and infarctions are widely formed in the gastrointestinal tract due to necrotizing arteritis.

Polymyositis prevention

Reasonably match the diet and pay attention to adequate nutrition. Ensure adequate sleep, pay attention to rest, and improve your immunity.

Polymyositis complications Complications cough arrhythmia

Visceral complications of polymyositis

Compared with the incidence of visceral lesions in other connective tissue diseases (such as systemic lupus erythematosus, progressive systemic sclerosis), visceral complications of polymyositis (except pharyngeal and esophageal) are rare, but occasionally visceral involvement The performance appeared before the muscles were weak. Interstitial pneumonia (expressed as dyspnea and cough) can occur and can be a major clinical manifestation. According to reports, the incidence of cardiac involvement is gradually increasing, mainly due to abnormal ECG, such as arrhythmia, conduction disorder, and abnormal intersystolic phase. In some cases, acute renal failure occurs due to severe rhabdomyolysis, accompanied by myosinuria (squeezing syndrome). Some patients have Sjogren syndrome. Abdominal symptoms are more common in children, may have hematemesis or melena, caused by gastrointestinal ulcers, can develop into perforations, and therefore require surgical treatment.

Nearly 15% of men over the age of 50 and a few female patients have malignant tumors. Its type and location of the disease have no obvious features.

Symptoms of polymyositis Common symptoms Myasthenia gravis difficulty dysphagia Symmetrical muscle weakness Physical discomfort Joint pain Laryngeal muscle weakness Fever with joint swelling and pain

The onset can be acute or insidious. Acute infection can be a trigger for the performance or morbidity of its precursors. Adults and children have similar symptoms, but children are often very ill, and adults are mostly occult. Early symptoms are usually proximal muscle weakness or rash. (In inclusion body myositis, the distal muscles are also involved even more heavily than the proximal muscles). Muscle tenderness and pain are significantly less than muscle weakness. Skin rash, multiple joint pain, Raynaud's phenomenon, difficulty swallowing, lung disease and general malaise, fever, fatigue, weight loss, etc. can occur.

Muscle weakness can occur suddenly and continue to progress for weeks to months. It can destroy 50% of muscle fibers, causing muscle weakness (muscle weakness indicates progressive myositis). The patient had difficulty lifting the upper limbs over the shoulders, up the steps, and standing up from the seat. Due to the weakness of the pelvic and shoulder muscles, the patient needed to be in a wheelchair or bedridden. The cervical flexor can be severely affected and cannot be lifted from the pillow. Laryngeal muscle weakness is the cause of difficulty in pronunciation. The involvement of the chest wall muscles and diaphragm muscles can cause acute respiratory insufficiency. Pharyngeal, striated muscles at the upper end of the esophagus cause difficulty in swallowing and reflux. The lower esophageal and small intestines are weakened and dilated, which is indistinguishable from progressive systemic sclerosis. Hands, feet, face and other muscles are generally not tired. Limb contracture can occur in the chronic phase of the later stages of the disease.

The rash usually occurs in dermatomyositis, mostly dim erythema, with lavender periorbital edema as a characteristic skin change in the disease. Skin lesions are slightly higher than the skin, with a smooth surface or scaly, which can occur in the forehead, neck triangle, shoulder, chest, back, forearm, calf, elbow, medial malleolus and the proximal side of the proximal interphalangeal joint. The nail bed and the edge of the nail are congested. A characteristic desquamative dermatitis with skin cracking can often involve the temporal side of the finger. Skin damage can often completely resolve, but it can also leave brown pigmentation, atrophy, scars or white spots. Skin calcification can also occur, especially in children. Its distribution is similar to progressive systemic sclerosis, but tends to be more extensive (universal calcinosis), especially in patients who are untreated or inadequately treated.

About 30% of patients with myositis and dermatitis often have multiple joint pains, accompanied by joint swelling, joint exudate and non-teratogenic arthritis. These rheumatic pains are generally mild and occur more in J. o -1 antibody positive population. The incidence of Raynaud's phenomenon is particularly high in patients with polymyositis and other connective tissue diseases.

Multimyositis check

Laboratory tests are clinically helpful but lack specificity.

ESR is often increased.

A small number of patients have antinuclear antibodies or lupus cells, especially those with other connective tissue diseases. About 60% of patients are positive for anti-thymocyte antigen (RM-1) antibody or anti-thymocyte extract (Jo-1) antibody. The relationship between these antibodies and the pathogenesis of the disease is unclear, although the Jo-1 antibody is an important marker associated with fibrotic alveolitis and pulmonary fibrosis.

Elevated serum muscle enzymes, especially transaminase, creatine kinase (CR) and aldolase.

Regular examination of CK levels can help guide treatment; effective treatment can reduce elevated enzymes, whereas in patients with chronic myositis and extensive muscle wasting, muscle enzyme levels are normal even during active periods.

Diagnosis and differentiation of polymyositis

There are five main diagnostic criteria:

(1) proximal muscle weakness;

(2) characteristic rash;

(3) elevated serum muscle enzyme content;

(4) changes in muscle biopsy (often decisive);

(5) Special electromyography triad: spontaneous fibrillation potential and positive sharp wave and insertion irritability increased; active contraction showed multi-phase short-term potential; repeated high-frequency discharge caused by mechanical stimulation. Electromyography is generally monomorphic, so biopsy should be performed on muscles with abnormal EMG, usually deltoid and quadriceps, but in order to avoid sites that have been stimulated by EMG probes, The material should be taken on the contralateral limb. Even in patients with dermatomyositis and polymyositis, muscle biopsy is still necessary for final diagnosis and needs to be differentiated from some rare diseases such as inclusion body myositis and rhabdomyolysis after viral infection. After diagnosis, the doctor can give immunosuppressive therapy to some hormone-insensitive people. Sometimes a biopsy is needed to identify remyelitis recurrence and corticosteroid-induced myopathy. MRI can sometimes distinguish between areas of edema and inflammation to give a positive result, especially for children. For every adult dermatomyositis patient, it is necessary to carefully check for malignant tumors, but it is not recommended to perform a systemic, traumatic blind examination.

Differential diagnosis

Different from dermatomyositis.

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