Polymyositis - Dermatomyositis

Introduction to polymyositis-dermatomyositis Polymyositis-dermatomyositis (PM-DM) is a group of acquired inflammatory myopathy with subacute or chronic onset. The main pathological features are muscle fiber necrosis, regeneration and intermuscular inflammation. Cell infiltration, the cause of PM-DM is unknown, so far it is still a diagnostic diagnosis. Any inflammatory myopathy that can not find a clear infectious agent (such as viruses, bacteria, parasites, etc.) belongs to this disease category, so it is also called It is idiopathic inflammatory myopathy. Because this group of diseases respond well to corticosteroid treatment, it is speculated that its pathogenesis may be related to autoimmune abnormalities. The main clinical manifestations of polymyositis (PM) are diffuse inflammatory myopathy, which is mainly caused by weakness of the proximal limb, neck and pharyngeal muscles. If a typical rash is combined, it is called dermatomyositis (DM). About 1/3 of patients can be combined with other connective tissue diseases, and 1/10 of patients are associated with tumors. Polymyositis-dermatomyositis Kidney damage is seen in a small number of patients. basic knowledge The proportion of illness: 0.013% Susceptible people: no special people Mode of infection: non-infectious Complications: inorganic alkali skin damage

Polymyositis - the cause of dermatomyositis

(1) Causes of the disease

Virus infection (30%)

The etiology of PM and DM is unknown. It may be caused by infection of certain viruses in susceptible populations. The immune system is disordered, leading to inflammation of connective tissue mainly composed of skeletal muscle lesions. The study found that PM/DM and HLA-DR3, inclusion body myositis and HLA-DR1 children's DM is highly correlated with the C4 null gene. Coxsackie virus, mucovirus, paramyxovirus, echovirus, influenza virus, hepatitis B virus and other infections may trigger the onset of this disease.

Abnormal humoral immunity (30%)

The abnormality of humoral immunity is elevated by immunoglobulin and positive for autoantibodies. Among them, myositis-specific antibodies (pathogenic antibodies) are antibodies directed against the cytoplasmic antigen components of myocytes, such as anti-Jo-1 and anti-Mi-2. Anti-PL-7 antibody, etc., children's DM skin biopsy showed a phenomenon of complement membrane attack on the small blood vessel wall, suggesting that skin muscle damage is related to complement activation.

Abnormal cellular immunity (30%)

Cellular immune abnormalities include abnormalities in the number and amount of various cytokines. Immunopathology confirmed the infiltration of CD8+T monocytes around the necrotic muscle fibers, suggesting that muscle damage is mediated by cellular immunity.

(two) pathogenesis

The exact pathogenesis of this disease is still unclear. At present, a large number of data prove that genetic factors, viral infection, autoimmune mechanisms and drugs are related to the occurrence of this disease.

1. Genetic factors: There is a report of multiple diseases in this disease, and the patients with HLA-138, HLA-DR3, and HLA-DRW52 have high frequency, suggesting that there are genetic factors involved in the disease. HLA-DR3 and HLA- are generally considered. DRW52 is associated with adult and adolescent myositis, and myositis-specific antibody-positive myositis is strongly associated with HLA gene. It has been reported that HLA-B14 is more common in adults with collagen vasculitis, C4 null gene and children Dermatomyositis is clearly associated.

2. Infection factors: The infection of various pathogens (bacteria, viruses, fungi, protozoa, etc.) has been found to be associated with the occurrence of this disease, especially the infection of the virus and toxoplasma is closely related to the disease.

(1) Bacteria: Staphylococcus, Clostridium, rickettsia and mycobacteria have been reported to be associated with this disease. For example, Staphylococcus aureus can invade muscles and cause acute abscesses, which can cause inflammatory myopathy.

(2) Toxoplasma and spirochetes: It has been reported that patients with toxoplasmosis and spirochete infection may have certain manifestations of polymyositis-dermatomyositis, especially muscle lesions, and the patient's antibody titer against these pathogens increases, but from It is difficult to culture pathogens in the muscle tissues of these patients. Since some patients with myositis have early histological changes of acute inflammatory diseases, it is not excluded that dermatomyositis and/or polymyositis is a toxoplasma or spirochete. In the late stage of infection, it has been reported that after treatment with anti-toxoplasmosis drugs, the clinical symptoms of the patients are improved, the antibody titer is decreased, and some people hold the opposite opinion. The infection theory is still in the inquiry stage.

(3) Virus: Coxsackie virus can induce experimental viral myositis in animals. Human infection with influenza virus and Coxsackie virus can cause mild inflammatory myopathy, which is common in children, generally self-limiting, adult. Rarely, an echovirus syndrome is very similar to dermatomyositis, which can be seen in boys with X-linked agammaglobulin deficiency, but by electron microscopy in muscle fibers of dermatomyositis or polymyositis. The granules were not confirmed by virus isolation or elevated viral antibody titers, and the disease was not transmitted to the animals by injecting the skeletal muscle extract into the animals.

In addition, the following points indicate that viral infections are associated with idiopathic inflammatory myopathy (dermatomyositis and polymyositis). First, particles similar to small RNA viruses can be found by ultramicroscopic examination of inflammatory muscles. Second, several uncommon small RNA viruses (encephalomyocarditis virus) can cause acute myositis, which interacts with histidyl tRNA synthetase, which is the target antigen of several myositis-specific autoantibodies. Antibodies may represent a cross-reactivity phenomenon that increases the likelihood that the virus will start viral myositis and autoantibody production. Third, several small RNA viruses, including coxsackievirus and encephalomyocarditis, can cause Animals are acute, sometimes chronic myositis, similar to human myositis; Fourth, it has been reported that adenovirus has been isolated from an inclusion body myositis; fifth, studies on animals, individual patients and groups It indicates that retroviruses including human immunodeficiency virus (HIV) and human T-cell leukemia/lymphoma virus (HTLV-1) are associated with myositis, but it has not been confirmed that persistent viral infection is the cause of progressive myositis, only some indirect Evidence suggests that some further research and dermatomyositis (or) cases of polymyositis and inclusion body myositis of virus in initiating the disease, definitive evidence for further study.

3. Immune abnormalities: A large number of data prove that autoimmune response is closely related to the onset. The relationship between humoral immunity and the disease can be explained by the fact that patients with this disease often have polyclonal hyperglobulinemia, and some patients can be investigated in serum. A variety of anti-nuclear antibodies and anti-skeletal muscle myoglobin antibodies, the anti-Jo-1 antibody against the diagnosis of the disease is the antigen is the histidine tRNA synthetase in the muscle cell nucleus, can be measured by immunofluorescence There are IgG and IgM deposits on the blood vessel wall of the patient's skin and muscle, which indicates that the disease is involved in humoral immunity.

Cellular immunity plays an important role in the occurrence of this disease. The animal model of this disease can be caused by skeletal muscle immunization of rats. The lymphocytes of model rats are transferred to normal rats, which can cause the same focal polymyositis. The damage of the activated lymphocytes to the muscles, the lymphocytes infiltrated by the infiltrating lymphocytes in the muscle of the patient can produce lymphokines which are toxic to the cultured fetal muscle cells; of course, it also damages the autologous muscle cells. This can prove that T cells are involved in the development of myositis. The muscle biopsy specimens found that the cells infiltrated around the muscle cells are mainly CD8 T cytotoxic lymphocytes, which have HLA class II antigen molecules on the surface of the accompanying macrophages. , indicating that they have been activated, immunohistochemical techniques can show that muscle fiber necrosis is the role of these activated cells, including antibody-dependent cytotoxicity.

This disease often occurs in conjunction with other autoimmune diseases, and it also suggests that the disease is closely related to autoimmunity.

4. Drugs, Toxicues and Others: Certain drugs can cause diseases similar to myositis, such as cimetidine, chloroquine, colchicine, corticosteroids, ethanol, imipenem (tauganine), heroin, lov Statins, penicillamine, azidothymidine, etc. In some cases, colchicine caused vacuolar myopathy, AZT caused mitochondrial myopathy - these characteristics help identify, the relationship between other drugs and myopathy It is clear, but histological changes are not characteristic, and the distinction is more difficult. The most obvious example is corticosteroid myopathy, which complicates the treatment of early myositis. The diagnosis is mainly based on prednisone reduction (and Not increasing the dose) can significantly improve the symptoms, there is a group of drugs, represented by D-penicillamine, can cause myopathy, clinical and histological changes and idiopathic myositis, such as dermatomyositis or polymyositis It is indistinguishable, so the mechanism by which poisons and drugs cause myopathy is still unclear.

In summary, there is an immune abnormality in this patient. This abnormality is determined by certain genetic genes, or is caused by acquired factors such as infection, or a combination of the two. It is still to be further studied, but it can be considered as Immune damage is the basis of this disease.

The main pathological changes of muscle biopsy in this disease are infiltration of inflammatory cells and degeneration or necrotizing lesions of muscle fibers in affected muscle tissues. The inflammatory cells appearing mainly are lymphocytes, but other cells are also visible. In muscle cells or around the endomysium, and in DM they appear around small blood vessels, the degeneration of muscle fibers, such as the size of muscle fiber bundles and muscle fiber necrosis and regeneration, are more common than inflammatory cell infiltration, which is more common. The lesions of myofibers are more common near the fascia. In DM, especially in childhood DM, in addition to lymphocytic infiltration around the interstitial small blood vessels, there is hyperplasia of vascular endothelial cells and embolization in the lumen of the blood vessels. In chronic myositis with a long course of disease, inflammatory changes are often less obvious and mainly manifested as fibrosis and even fatty changes in muscle fibers and interstitial. Foreign materials are shown in the muscular pathology of 118 cases of myositis. % muscle fiber destruction and regeneration, accompanied by infiltration of inflammatory cells, 8% only muscle fiber changes, 11% only muscle atrophy changes, 17% showed normal tissue.

The main feature of inclusion body myositis is the presence of vacuoles or inclusions in the muscle tissue. Myositis with malignant tumors often does not see muscle myositis.

Polymyositis - dermatomyositis prevention

Its pathogenesis may be related to autoimmune abnormalities, and there is no effective prevention method for autoimmune diseases. Prevention of infection, cold, and cold or hot induced factors are the key points of prevention and treatment; prevention and treatment of complications is also an important part of clinical medical care.

Polymyositis - dermatomyositis complications Complications, inorganic alkali skin damage

Polymyositis is an autoimmune disease characterized by muscle weakness and myalgia. It mainly involves the limb muscles, the neck muscles, and the throat muscles. If the skin is involved at the same time, it is called dermatomyositis. 40-year-old women, some patients may have a history of infection before the disease, with symmetrical limb proximal muscle weakness, pain and tenderness, may involve the pharyngeal muscles, respiratory muscles and neck muscles, late muscle atrophy, and some with skin Or visceral damage, or malignant tumors.

Polymyositis-dermatitis symptoms common symptoms morning stiffness proteinuria blockage fever hypothermia congestion

1. Muscle lesions: manifested as muscle weakness, myalgia, muscle tenderness and muscle atrophy. Among them, sympathetic progressive muscle weakness is most prominent. The proximal limb muscles, the cervical muscles and the pharyngeal muscles are common affected muscle groups. Walking obstacles, difficulty raising your arms, serious people can not comb and dress, if the eye, throat, throat, esophagus, sputum, intercostal muscle involvement, double vision, strabismus, hoarseness, difficulty swallowing, difficulty breathing, myocardial Arrhythmia and heart failure can occur with involvement.

2. Skin lesions: Skin lesions may occur at the same time or earlier or later than muscle symptoms. The rash includes:

(1) Gottron sign: red squamous maculopapular rash on the metacarpophalangeal joint and proximal knuckle. After a long time, the center is atrophy and hypopigmentation. The intrinsic DM is a specific rash with a diagnostic value, and the incidence rate is about 70%.

(2) positive rash (heliotrope rash): red edematous rash appears in the periorbital gyrus, the above sputum is the main, about 50% of the early signs can appear, also one of the DM characteristic rash.

(3) rash on the exposed area: 30% of the face, neck, chest V-shaped area, neck shawl and red rash on the exposed parts of the extremities, with telangiectasia, some sensitive to light.

(4) Skilled hand: 1/3 of the patient's hands and palmar skin appear keratinized, cracked, desquamation, similar to the hands of professional mechanics operators.

3. Other manifestations: irregular hypothermia, may occur for initial symptoms or in the course of the disease, 20% with joint lesions, mainly joint pain, secondary to adjacent muscle contracture, can cause joint deformity and limited mobility, 20% ~30% of Raynaud's phenomenon, a few cervical lymph nodes can be swollen, involving the heart, tachycardia, atrial fibrillation, myocardial damage, heart enlargement and heart failure. Severe cases of pleurisy, interstitial pneumonia and decreased lung function, Among them, lung function damage is often the main cause of death. About 1/3 of cases have mild to moderate swelling of the liver. Digestive tract barium meal can show poor esophageal peristalsis, dilatation and retention of piriform sputum, retinal exudation, hemorrhage, choroid Inflammation and so on.

4. Primary polymyositis: About 1/3 of patients with inflammatory myopathy, usually insidious onset, slowly progressing in weeks, months, and years, only a few patients with acute onset within a few days Severe muscle weakness, or even rhabdomyolysis, can be seen at any age, women are more common than men, the ratio of male to female is 1:2.

(1) General performance: patients may have chills, moderate or low fever, fatigue, weakness, loss of appetite, weight loss, a few patients may have joint pain in the extremities, individual patients with arthritis as the first symptom, accompanied by morning Stiff, but the joint swelling is generally less than 6 weeks, no joint deformity, need to be differentiated from rheumatoid arthritis, such as the patient's hand deformed, usually caused by muscle spasm, no obvious joint damage, a few patients may have Raynaud's phenomenon, manifested as When the emotion is excited or cold, the finger (toe) is pale, cyan, and flushed.

(2) Muscle performance: This disease usually involves striated muscle. The patient first feels weakness in the proximal and neck muscles of the extremities. Generally, the two sides are symmetrical. When the patient has pelvic girdle and lower extremity muscle weakness, it can be upstairs and uphill. Difficulties, squatting or standing up from the seat, gait, squatting, feeling weak in the lower limbs when walking, when the scapula or the proximal muscles of the upper limbs are involved, it may be difficult to lift the arms, can not comb and dress, the neck muscles are weak It is difficult to raise your head when lying down, respiratory muscle weakness can cause chest tightness, shortness of breath, difficulty breathing. In severe cases, you need to use the ventilator to assist breathing. The throat or upper esophage striated muscle may cause difficulty in swallowing. Causes cough and aspiration, the orbicularis and facial muscles are rare, which helps to identify with myasthenia gravis, symmetrical proximal muscle weakness is the characteristic of this disease, but patients can have different degrees of limbs throughout the course of the disease The distal muscles are unable to perform. The physical examination needs to confirm whether the individual muscles or muscle groups are weak. The severity of muscle weakness should be recorded in each follow-up. The quantitative estimation of muscle strength is one for the patient. Important measurement indicators, because laboratory indicators do not always accurately reflect disease activity, there are several grading methods for the severity of muscle weakness, Rose and Walton's method combines physical examination with muscle function, simple and easy, and There is also a method for rapidly evaluating the muscle strength of the lower limbs according to age and gender standards. An improved sphygmomanometer detection method can be used to measure the muscle strength of the shoulder abductor muscle, which is simple and reproducible, and can be used for measurement of other muscle groups. A hand-held dynamometer measures the muscle strength of multiple muscle groups.

In addition to muscle weakness, 25% of patients may be associated with myalgia and/or muscle tenderness. A few patients have only myalgia and no muscle weakness. The diagnosis of such patients must be highly cautious, sometimes the patient is only weak and needs careful The test can find its muscle weakness.

With the prolongation of the disease, the patient may have different degrees of muscle atrophy. The muscle texture of the early lesions may be normal, and the muscles may become hard after fibrotic changes. The rare violent patients present with rhabdomyolysis, myoglobinuria, and renal failure. .

(3) Pulmonary manifestations: interstitial pneumonia, pulmonary fibrosis, pleurisy is the most common lung disease of polymyositis, which can occur at any time during the course of the disease, manifested as chest tightness, shortness of breath, cough, sputum, breathing Difficulties, purpura, etc., a small number of patients have a small amount of pleural effusion, but a large number of unilateral pleural effusion is rare, need to pay attention to the identification of tuberculosis or tumor, due to esophageal dyskinesia, difficulty swallowing, laryngeal reflex, often cause aspiration pneumonia, lung not Zhang et al., such as patients with respiratory muscle weakness, difficulty in draining, easily lead to bacterial growth, due to the use of immunosuppressants, often secondary to bacteria, mold and tuberculosis infection, so lung involvement is a common cause of death of polymyositis One.

(4) cardiac performance: 50% of patients have heart involvement, mainly myocarditis and pericarditis, endocarditis and myocardial infarction are rare, patients can be expressed as palpitations, shortness of breath, chest tightness, precordial discomfort, difficulty breathing, patients can There are pericardial effusion, heart enlargement, cardiomyopathy, arrhythmia, conduction block, etc. Late congestive heart failure and severe arrhythmia are one of the main causes of death in patients.

(5) Kidney disease: patients may have proteinuria, hematuria, tubular urine, rare fulminant polymyositis may be manifested as rhabdomyolysis, myoglobinuria, renal failure, renal biopsy may have local immunoglobulin And complement deposition, which is focal glomerulonephritis, suggests that immune complexes may be the cause of kidney damage.

5. Primary dermatomyositis: In addition to the above-mentioned manifestations of myositis, the patient has a characteristic rash, 55% of patients with rash appear before myositis, 25% with myositis, and 15% after myositis.

(1) Myositis manifestation (see "Primary polymyositis").

(2) Skin manifestations: Common skin manifestations of dermatomyositis are:

1 positive rash (heliotrope rash): edematous dark purple erythema appearing in the upper eyelid or periorbital, may be one or both sides, there may be telangiectasia near the temporal margin, sensitive to light, such rash It can also appear in the cheeks, nose, neck, chest V-shaped area and upper back, seen in 60% to 80% of patients with dermatomyositis, a characteristic rash of dermatomyositis.

2Gottron's papules: a red or purple-red maculopapular rash of rice-to-mung bean size with margins that can be fused into a piece with skin atrophy, telangiectasia and hyperpigmentation or diminution, occasionally skin ulceration Such skin lesions appear on the joint surface, especially the metacarpophalangeal joint and the interphalangeal joint extension surface, and can also appear on the elbow, knee joint extension surface and internal hemorrhoids, with clear boundaries, surface covered with scales or local edema. It can occur in 60% to 80% of patients with dermatomyositis, which is another characteristic lesion of the disease.

3 periungual lesions: telangiectasia erythema can be seen at the nail folds, or defects appear, wrinkles and nail beds have irregular thickening, and a week can be linear congestive erythema, localized pigmentation or pigmentation.

4 "Mechanic hand" sample change: dirt on the palm and side of the finger, dark horizontal lines across the finger, because it is similar to the long-term manual operation of labor, hence the name "technical hand."

5 other skin mucosal changes: 20% of patients may have Raynaud's phenomenon, caused by changes in nail fold microcirculation, finger ulcers, peri-infarction and other cutaneous vasculitis manifestations may also appear, suggesting the potential for malignant lesions, oral mucosa Erythema can also occur, 75% to 80% of patients may have photoallergies, muscle induration, subcutaneous nodules, subcutaneous calcification changes.

6. Malignant tumor-associated dermatomyositis or polymyositis: In 1935, Ringel et al first reported that myositis was associated with malignant tumors, and subsequent observations suggest that patients with polymyositis-dermatomyositis have malignant tumors. The risk is significantly increased. Some people think that patients with dermatomyositis are more likely to have tumors than patients with polymyositis. Although the muscle and skin changes in this group are not significantly different from those in other groups, they have been divided independently, accounting for about 10% of all cases. % (6% to 60%), patients may have malignant tumors first, followed by polymyositis or dermatomyositis, and some patients develop malignant tumors after several years of polymyositis or dermatomyositis, occasionally two The lesions occur simultaneously in 1 year and have parallel course. Early studies suggest that ovarian cancer and gastric cancer are the most common, and other tumors may also appear, such as lung cancer, breast cancer, digestive tract cancer, hematological malignancy, thyroid cancer, nasopharyngeal carcinoma. , kidney cancer, etc.

Generally, it is rare in children with myositis and myositis associated with connective tissue disease. The incidence of tumors in patients over 40 years old is high, especially in elderly patients over 60 years old. Therefore, detailed medical history and comprehensive physical examination of such patients are very Important, especially for breast, pelvic, rectal examination can not be ignored, can also be combined with the corresponding auxiliary examination, such as blood routine, biochemistry, blood protein electrophoresis, carcinoembryonic antigen, immunological examination, urinary red blood cells and cytology analysis, Occult blood, chest X-ray, sputum cytology, bone scan, B-ultrasound, etc., in order to find clues about tumor diagnosis, if necessary, can carry out gastrointestinal angiography, cervical smears, etc., type of malignant tumors in patients with myositis and The location is related to gender and age.

Some authors have suggested that myositis is a paracancerous syndrome, and its onset may be related to changes in the immune status of the body, cross-reactive antigens between tumors and muscles, or potential viral infections in the muscle itself.

7. Childhood dermatomyositis or polymyositis: childhood dermatomyositis or polymyositis accounts for 8% to 20% of patients with myositis. There is often a history of upper respiratory tract infection before onset, no Raynaud phenomenon, rarely Pulmonary interstitial fibrosis and malignant tumors occur mostly in 5 to 14 years old, and the ratio of male to female is 1.3 to 2:1. Although occasional cases of childhood and adult polymyositis are similar, the observed childhood inflammation is usually observed. The process of myopathy is unique. The general manifestations of childhood dermatomyositis are rash and muscle weakness, but due to the presence of vasculitis, ectopic calcification and lipoatrophy, it is very different from adult performance.

(1) Skin manifestations: usually the child first appears skin manifestations, then muscle weakness, rash is generally more typical, is the erythema located in the ankle and elbow, fingers, knee joints, can have desquamation, pigmentation and pigmentation Loss, congestive papules may occur in the periorbital period, and patients with severe acute phase may have cutaneous vasculitis, such as skin ulcers, peri-infarction, and the presence of these symptoms may indicate a potentially malignant lesion.

(2) Muscle manifestations: muscle weakness, muscle pain and stiffness in the proximal muscles and neck flexors are obvious, but can also be diffuse, affected muscles have tenderness and swelling, skin damage and muscle weakness in childhood dermatomyositis Almost at the same time, but the severity and progress of the two manifestations have greater individual differences, severe muscle weakness can lead to difficulty in chewing, hoarseness, difficulty swallowing and breathing, and even respiratory failure.

(3) vasculitis: some children can be completely relieved without treatment, but in severe cases with vasculitis, although treatment can not prevent disease progression, vasculitis can also cause gastrointestinal ulcers, bleeding or perforation .

(4) ectopic calcification: ectopic calcification can occur in the skin, subcutaneous tissue, muscle or fascia, can be diffuse or localized, some patients with subcutaneous calcification and vasculitis at the same time, some children only subcutaneous Calcification, calcification can cause ulcers in the skin, affecting the posture of the child, and long-term muscle weakness, muscle contracture, can affect mobility.

(5) Other manifestations: some patients may have pericardial effusion and pleural effusion, electrocardiogram may show conduction block changes, acute phase may have retinal edema and hemorrhage, optic nerve fiber damage, optic atrophy, visual field loss or transient retinal detachment Individual patients may have thrombocytopenia, peripheral neuritis, seizures and subarachnoid hemorrhage.

Despite children's dermatomyositis, polymyositis has a better prognosis than adults, but the death toll is still 1/3 of the total number of patients.

8. Other connective tissue disease-associated polymyositis or dermatomyositis: About 1 in 5 patients with myositis are associated with other connective tissue diseases, forming overlapping syndromes. This overlap may be caused by some inherent cause. Rather than being randomly stacked, the common overlapping diseases are systemic lupus erythematosus, rheumatic polymyalgia, Sjogren's syndrome, rheumatoid arthritis, mixed connective tissue disease, nodular polyarteritis, Weg Nasal granulomatosis, giant cell arteritis, allergic granuloma, hypersensitivity vasculitis, etc., diagnosis depends on the respective diagnostic criteria of the two types of rheumatism, and sometimes the clinical manifestations of idiopathic inflammatory myopathy may become such The prominent features of the patient, especially when myositis and systemic sclerosis, systemic lupus erythematosus, rheumatoid arthritis, mixed connective tissue disease and Sjogren's syndrome coexist, but vasculitis syndrome is rare, muscle weakness at this time Often associated with arteritis and nerve involvement, but not with non-suppurative inflammatory changes in the muscle.

On the other hand, some patients with connective tissue disease often show signs of muscle weakness and other myopathy, such as elevated levels of serum creatine phosphokinase and typical EMG changes, making it difficult to distinguish from typical polymyositis. Some patients, however, have muscle weakness, but are not associated with increased levels of muscle enzymes and changes in EMG.

Muscle histological changes in patients with myositis secondary to another diffuse connective tissue disease may be the same as in patients with polymyositis, but some patients may have different performance characteristics, such as muscle lesions in patients with scleroderma It is characterized by different sizes of muscle fibers, occasional necrosis of individual muscle fibers, connective tissue hyperplasia in and around the muscle bundle, and mononuclear cell infiltration in the perivascular vessels. Muscle histological changes in patients with systemic lupus erythematosus are similar to those in adult dermatomyositis Congestive inflammatory changes are rare in rheumatoid arthritis, and are rare in Sjogren's syndrome. Common type 2 fibrous atrophy and non-specific changes or normal muscle structure are only accompanied by a small amount of lymphocytic infiltration in patients with severe rheumatoid vasculitis. Occasionally, arteritis changes in muscle tissue can be seen, and the muscle pathology of patients with mixed connective tissue disease can be the same as dermatomyositis or scleroderma.

In some patients, muscle weakness may be related to side effects of therapeutic drugs, such as glucocorticoids, D-penicillamine and antimalarials. Some patients may be due to the action of cytokines such as interleukin-1, leukocyte Cy165, tumor necrosis factor, etc., need to pay attention to identification.

9. Inclusion body myositis: Because this is a rare disease, many doctors lack experience in diagnosis, so the exact prevalence rate is still unclear. It is reported that these patients account for about 15% of all inflammatory myopathy. %28%, generally distributed, no family aggregation tendency, children are rare, less common under 40 years old, mostly in elderly patients, often insidious onset, slow progress, long course of disease, some cases have existed before the diagnosis of symptoms 5 6 years, its clinical manifestations and polymyositis have many similarities, the difference is that typical polymyositis is characterized by muscle weakness can be focal, distal muscles can also be affected, and often two Lateral asymmetry, obvious early finger or forearm flexor and calf extensor involvement, often characteristic, myalgia and muscle tenderness are rare, generally no rash, 20% of patients in the late stage may have difficulty swallowing, sometimes the symptoms are very obvious, Facial muscle weakness is rare, there is no report of drooping eyelids or ophthalmoplegia, and the cardiovascular system is similar to polymyositis.

With the gradual increase of muscle weakness, muscle atrophy and deep sputum reflex can be weakened. In some patients, the disease can progress slowly and slowly. In some patients, the disease is still in the weakness and atrophy of some muscles, and there is no inclusion body myositis and tumor coexisting. Reported, but sometimes combined with the following diseases: interstitial pneumonia, scleroderma, systemic lupus erythematosus, dermatomyositis, Sjogren's syndrome, immune thrombocytopenia, sarcoidosis, psoriasis, diabetes, etc. The frequency of coexistence of disease and inclusion body myositis is not high, and its significance is still unclear.

This disease usually does not respond well to treatment with glucocorticoids and immunosuppressive agents, but in some patients, the condition can be improved after intravenous administration of immunoglobulin, a chronic progressive disease that occurs 5 to 10 years after onset. The patient may lose walking ability.

10. Other myositis:

(1) eosinophilic myositis: this is a rare type of disease that may represent one of the manifestations of eosinophilia syndrome, characterized by subacute onset, may have proximal muscle weakness and Myalgia, elevated levels of serum muscle enzymes (especially creatine phosphokinase, etc.), myoelectric changes in myocardium, histopathology in addition to myositis changes, eosinophil infiltration is characteristic, some patients The response to glucocorticoids, methotrexate or leukocyte replacement therapy is good, and the disease includes several different subclasses.

1 eosinophilia syndrome (eosinophilia-myalgia syndrome) see scleroderma.

2 eosinophilic faitis (eosinophilic faciitis) see scleroderma.

3 relapsing eosinophilic perimyositis (relapsing eosinophilic perimyositis) The disease is characterized by neck and lower extremity muscle pain and tenderness, but no muscle weakness, often increased ESR, peripheral blood eosinophilia, Serum creatine phosphokinase is sometimes elevated, histological examination showed that the fascia membrane has eosinophil infiltration, and the response to glucocorticoid therapy is good.

(2) focal nodular myositis: this is an acute syndrome, manifested as focal inflammatory pain nodules, sometimes in different muscles, called focal nodular muscle Inflammation, pathological manifestations and response to treatment are similar to polymyositis. When presented in a single appearance, attention should be paid to the identification of muscle tumors (sarcoma or rhabdomyosarcoma) or proliferative fasciitis and myositis. Note the differentiation of muscle infarction with nodular polyarteritis.

Examination of polymyositis-dermatomyositis

Auxiliary inspection:

1. Serum CPK, LDH, GOT increased, serum myoglobin content increased significantly, serum protein electrophoresis , r globulin and serum IgG, IgA, IgM increased. More than half of the patients have a rapid blood loss.

2. 24-hour creatinine excretion in urine can be significantly increased, >1000mg / 24 hours, and is related to the severity of the disease.

3. Electromyography: the insertion potential is prolonged, and there may be muscle strong and straight discharge activity. When the light contraction, the average amplitude of the motor unit potential is reduced, the time limit is shortened, and there may be a large number of fibrillation waves, multiphase waves increase, and low amplitude interference occurs during heavy contraction. Phase or pathological interference phase.

4. Muscle biopsy: showing degeneration, necrosis, inflammatory cell infiltration, muscle fiber swelling, glass-like, granular or vacuolization, interstitial edema, infiltration of perivascular lymphocytes and plasma cells.

5. Electrocardiogram: abnormal rate can reach about 40%, tachycardia, myocardial inflammation, or arrhythmia.

Diagnosis and differentiation of polymyositis-dermatomyositis

Diagnostic criteria

1. Classification of dermatomyositis: There is currently no satisfactory classification method for dermatomyositis, generally using the classification proposed by Bohan and Peter (1975):

(1) Polymyositis, accounting for 30% to 40%.

(2) Dermatomyositis, accounting for 20% to 30%.

(3) polymyositis-dermatomyositis with malignant tumors, accounting for 10% to 15%.

(4) Children's dermatomyositis, accounting for 10%.

(5) Overlap syndrome (dermatomyositis or polymyositis combined with other connective tissue diseases), accounting for 20%.

2. Children's dermatomyositis is divided into two types, rarely associated with visceral malignant tumors.

(1) Brunsting type (type II): more common, characterized by chronic course, progressive myasthenia, calcareous and corticosteroids; clinical manifestations are very similar to adult dermatomyositis, the main difference between the two is Calcareosis occurs in 40% to 70% of children, and childhood cases are rarely associated with potentially malignant tumors.

(2) Banker type (type I): rare, characterized by rapid onset of severe muscle weakness, muscle and gastrointestinal vasculitis, poor efficacy of corticosteroids, and high mortality.

3. Diagnostic criteria generally use the diagnostic criteria for polymyositis-dermatomyositis proposed by Bohan and Peter (1975): a clear diagnosis can be performed with magnetic resonance imaging. The diagnostic criteria for DM and PM are as follows:

(1) Limbs muscles: (shoulders with muscles, pelvic muscles, proximal limbs muscles) and anterior flexors of the neck are weak and weak, and there are fashionable dysphagia or respiratory muscle weakness.

(2) Muscle biopsy shows that the affected muscle has degeneration, regeneration, necrosis, phagocytosis and infiltration of mononuclear cells.

(3) Serum muscle enzymes, especially CK, AST, LDH and so on.

(4) EMG is myogenic damage.

(5) typical skin rash; including upper eyelid purple red spot and periorbital edematous purple red spot; Gottron sign of metacarpophalangeal joint and dorsal side; perivascular vasodilation; elbow and knee joint extension, upper chest "V" The erythema scaly rash and skin color lesions in the word area.

Diagnosed DM: has the first 3 to 4 criteria plus the fifth.

Confirmed PM: Has the first 4 criteria but no 5th performance.

Probably DM: has 2 criteria and 5th.

May be PM: There are 2 criteria but no 5th.

Differential diagnosis

Need to be differentiated from muscular dystrophy, thyroid dysfunction, systemic lupus erythematosus.

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