What Is the Difference Between Dermatomyositis and Polymyositis?

Skin and muscle are the two main groups of symptoms. Skin often develops weeks to years before muscles, and may also precede myositis or muscles and skin. Skin and muscle symptoms are often not parallel, but one is heavy and the other is lighter. In some cases, the organs that first show symptoms may not be skin or muscle, but heart, lung, or pleura, which manifest as cardiac tamponade, pulmonary fibrosis, or pleurisy.

Dermatomyositis and Polymyositis

Dermatomyositis (DM) and polymyositis (PM) are currently considered to belong to the category of autoimmune diseases. DM shows diffuse inflammation of the skin and muscles, erythema and edema appear on the skin, muscles show weakness, pain, and swelling, which can be accompanied by joint pain and multiple organ damage such as lungs and myocardium; PM has no skin damage. This disease is similar to TCM muscle paralysis or rheumatism. Like Huangdi. The Nei Jing · Su Wen Long Section Acupuncture Chapter records: "The disease is on the skin, the skin is painful, the name is muscle paralysis, and the injury is cold and damp." The origins of various diseases: Rheumatism, the hands and feet of the body are not waiting: "The rheumatism and cold air are combined to become paralysis .... Those with more rheumatic air are also known as rheumatism. Those who are debilitated by the rheumatism will be injured by rheumatism. As for the blood, if the blood doesn't work, then it will not be declared. The true and evil are between the muscles, so the skin hurts. "

Dermatomyositis and polymyositis signs

1. Skin symptoms Typical skin lesions are edematous mauve spots on the upper eyelids, which spread to the orbit and gradually expand to the V-shaped area of the face, neck, and upper chest (Figures 1 to 3). Limbs, elbows and knees, especially the metacarpophalangeal and phalangeal (toe) joints, have purple-red papules, with telangiectasias, hypopigmentation, and overlying small scales, called Gottron (Gordon) sign or Grottron papules. The edematous purplish spot and Gottron sign of the upper eyelid are important basis for the diagnosis of DM, especially the former, which appears earliest and is of great significance for early diagnosis. In most patients, the skin lesions are painless and itchy.

Other types of skin damage in DM include heterochromia, erythroderma, cutaneous vasculitis, urticaria, and calcium deposits. The possibility of skin heterochromia accompanied by malignant tumors increases; skin vasculitis and skin calcium deposits mostly occur in JDM, and those with cutaneous vasculitis tend to have systemic vasculitis at the same time, often with severe symptoms and poor prognosis when not treated properly. ; People with skin calcium deposits often have important organ damage and have a good prognosis, but there have been reports of extensive abdominal calcium deposits causing acute abdomen and intra-abdominal bleeding. The types of skin lesions that rarely occur are plaque-like mucin deposits and blisters or bullae damage. Mucin deposits tend to occur in middle-aged and elderly women and can be the first symptom of DM; blisters or bullae have poor prognosis.

2. Muscle symptoms involve striated muscle, but skeletal muscle involvement is much more common than cardiac muscle; smooth muscle is rarely affected. The proximal muscles of the extremities are most vulnerable, such as the deltoid and quadriceps. Polysymmetric onset. The diseased muscles have symptoms such as weakness and pain, and show corresponding movement disorders, such as difficulty in raising the upper limbs, inability to lift the lower limbs, and stand up after squatting; heavier people have difficulty raising their heads and cannot turn over, showing the neck and trunk muscle groups In severe cases, the limbs cannot move on the bed or can only move a few centimeters, and even slight muscle contraction is not seen. Esophageal and throat muscles may have difficulty swallowing, coughing after eating, and changes in pronunciation. Breathing muscles may be short of breath and dyspnea. Eye muscle involvement has diplopia. A few patients may have myalgia without muscle weakness.

3. Other system symptoms

(1) Digestive system: Symptoms of the digestive tract are most common in systemic damage, manifested as bloating, decreased appetite, digestion and malabsorption, constipation or diarrhea. Nearly a third of the patients had difficulty swallowing, mainly due to difficulty swallowing solid foods; Barium meal imaging of the esophagus was performed in the supine position, and abnormalities such as esophageal dilatation, poor peristalsis, slow passage of the contrast agent, and pear-like appearance Nest barium retention. JDM can also cause intestinal necrosis due to vasculitis, gastrointestinal ulcers and bleeding. Liver dysfunction is more common during disease activity. Individual patients may have gallbladder sclerosis and cholestatic hepatitis, at which time anti-mitochondrial antibodies can be detected.

(2) Respiratory system: The common lung diseases are: interstitial pneumonia (ILD), the incidence is> 40%; alveolitis (> 30%) and bronchial pneumonia caused by ventilation disorders (about 20%). It develops slowly, may have different degrees of dyspnea, and is prone to secondary infection. According to foreign statistics, the incidence of DM / PM in the above three lung diseases is 40%, and the mortality rate is 27%. It is considered that high levels of aspartate aminotransferase (AST), ferritin, and anti-Jo-1 antibodies are positive in serum and characteristics. Sexual microangiopathy can help determine lung disease and estimate prognosis. Non-invasive early detection of the above lung lesions can rely on high-resolution CT (HRCT) and pulmonary function tests to find asymptomatic patients with pulmonary fibrosis more than X-rays. Carbon monoxide diffusion function (DLCO) test is the most sensitive in pulmonary function test, and it can detect early patients who have not changed in imaging, especially alveolitis, which can not be detected by HRCT.

A small number of patients with pulmonary interstitial lesions appear as acute type, which can occur at any stage, manifested as acute fever, dyspnea, cyanosis, dry cough, and muscle weakness symptoms may not be obvious, respiratory failure will occur quickly, and the prognosis is poor. The serum levels of creatine phosphate (CK) in these patients are usually normal, but the AST is significantly increased, and the ratio of CK to AST is decreased. Peripheral white blood cells are reduced, and the absolute lymphocyte count is low. The lymphocytes in bronchial lavage fluid are significantly increased. Patients with muscle involvement can also develop aspiration pneumonia; pleurisy can also occur; individual pneumothorax, mediastinal gas, and even extensive subcutaneous emphysema can occur.

(3) Heart: Heart disease becomes more frequent. About 50% of abnormalities can be found, but most of them are mild. Only ECG shows ST-T changes. Others include arrhythmia and various degrees of conduction block, and mitral valve prolapse is also more common. Very few patients have heart failure and severe arrhythmia due to myocardial disease. At this time, the prognosis is poor. Most of these patients have systemic scleroderma. Most patients are sensitive to corticosteroid treatment, and ECG abnormalities can recover as muscle / skin symptoms improve.

(4) Kidney: Renal lesions are mild and rare (except those with other CTD), and there may be a small amount of proteinuria, cast urine and hematuria.

4. Special type

(1) JDM: Children's PM is rare, mostly JDM. The age range of JDM is 4 to 15 years. According to Pachman LMZ's statistics of 79 cases of JDM in 1998, the symptoms of the patients were: erythema of the skin 100%, weakness of the distal muscles 100%, muscle pain 73%, fever 65%, difficulty swallowing 35%, and hoarseness 34% , Abdominal pain 29%, joint pain 28%, skin calcium deposits 18%, melena 10%; 10% muscle enzymes are normal in laboratory tests, 8% electromyogram is normal, and 10% muscle biopsies are normal; average from symptoms to diagnosis For 2 months. Different from adult DM / PM, JDM is mostly related to infection. The clinical manifestations are more acute, severe vasculitis, and prone to skin calcium deposits. Among them, patients with acute exacerbation, severe swallowing difficulties, high fever with leukocytosis, gastrointestinal ulcers, and severe vasculitis are not sensitive to corticosteroid treatment, and need to add cytotoxic drugs, and the prognosis is poor. However, those with chronic organ damage, vasculitis, and other organ damage without or mild skin calcification are sensitive to corticosteroid treatment and have a good prognosis.

(2) Overlapping syndrome (OLS): DM or PM can overlap with other CTDs. Often combined with systemic scleroderma (common acromosis), systemic lupus erythematosus, rheumatoid arthritis and Sjogren's syndrome, polyarteritis and so on. Especially overlap with scleroderma, so Raynaud's phenomenon (RP) often appears before muscle symptoms. OLS is two diseases that appear in the same patient, so the diagnosis of OLS should be based on their own diagnostic criteria. For example, although scleroderma can have muscle weakness, muscle atrophy and fibrosis can be seen on muscle biopsy, but there is no inflammatory cell infiltration, and serum muscle enzymes are normal; muscle symptoms of SLE can also be quite obvious, and muscle biopsy is similar to myositis, but both The types of autoantibodies are different. The incidence of malignant tumors in patients with myositis is low. The incidence of cardiomyopathy is high in patients with scleroderma.

(3) With tumors: The incidence of adult DM / PM combined tumors is high, especially for DM, which is more than 1 times higher than PM, especially for patients> 50 years old. Tumors can occur at the same time as DM, but it is more common to have skin and muscle symptoms first, and then to find malignant tumors months or even years later. Therefore, systemic examination should be performed on DM with poor treatment effect and middle-aged or older to exclude tumors. In contrast, those with severe damage to the lungs and other organs, and those with other CTDs are less likely to have tumors. A few patients have typical myositis clinically, but muscle biopsy fails to find typical pathological changes, and even CK does not increase. Such patients may be more likely to have tumors. As for which tumor is most likely to accompany DM / PM, it varies from country to country and region to nation.

(4) amyopathic dermatomyositis (ADM): ADM is characterized by skin manifestations of typical dermatomyositis but lacking myositis. The longest time that Chinese people have followed ADM is Fung WK in Hong Kong, with a period of 20 to 90 months (average 35.6 months). A total of 6 cases were observed, of which 5 cases had malignant tumors (3 cases of nasopharyngeal carcinoma, 1 case of non-small cell lung cancer, and 1 case of cervical lymph node metastasis of unknown origin). Lam WWM, Department of Imaging Diagnosis and Organ Imaging, The Chinese University of Hong Kong, conducted magnetic resonance imaging (MRI) examinations on 10 patients with clinical diagnosis of "ADM", of which 3 showed muscle inflammation; 6 patients found tumor lesions. Therefore, "non-myopathy dermatomyositis" is not exactly as it is called "dermatomyositis-like dermatitis" may be more accurate. Most of the ADM is related to malignant tumors, which are the skin manifestations of "skin-tumor syndrome" or "paraneoplastic syndrome"; a small part are DMs that have not yet developed muscle symptoms or skins with chronic skin-type lupus erythematosus or other CTD Allergic dermatitis caused by chemical substances such as damage, drugs, or light is confused and the cause is very rare in a very small number of patients.

(5) Jo-1 syndrome (JS): JS is an independent disease or a subtype of PM / DM. Its characteristics are:

Severe pulmonary interstitial lesions can occur before or after the myositis is cured.

Relatively mild polyarthritis, high titer of RF, a few can be erosive joint disease as RA;

mild myositis.

Anti-Jo-1 antibody was positive.

Fever, Raynaud's phenomenon, serositis, elevated white blood cells, dry skin, and cleft palate.

In addition, there can be HLA-DR3 / -DRw52 marking. The treatment of JS is mainly based on pulmonary interstitial lesions, and the response to treatment is poor.

Dermatomyositis and polymyositis medication

The acute phase must be bedridden, with passive movements of limbs and joints on the bed. Avoid colds, infections, and pregnancy. Give a high-protein diet. Those who have difficulty swallowing should raise the bedside while sleeping. Appropriate exercise should be performed after the condition is stable. Those with severe skin lesions should also avoid sunlight.

1. For the treatment of primary lesions As the etiology of some patients, especially DM, is related to tumors, they should be actively sought. In particular, patients with severe skin lesions and relatively mild myositis or those with negative anti-Jo-1 or anti-Mi-2 antibodies must undergo a systematic examination. For those who do not respond to long-term formal treatment, tumors should be ruled out. If the tumor can be removed in time, muscle and skin symptoms can be quickly recovered with a small amount of corticosteroids. The cause of JDM is related to infection. Early treatment with antibiotics should be supplemented with anti-gram positive bacteria drugs.

2. Corticosteroid treatment Corticosteroid is still the drug of choice for this disease, the dosage and usage depend on the degree of muscle disease and organ damage of the patient. You should give a full dose when starting treatment, do not increase the amount of "climbing". It is equivalent to 1 to 1.5 mg / kg of prednisone per day. It should be administered intravenously to those with cough and dysphagia. Because fluorinated corticosteroids such as triamcinolone, triamcinolone, betamethasone, and dexamethasone can easily cause hormonal myopathy, they should be avoided. "High-dose corticosteroid intravenous shock therapy" is not suitable.

In most patients, symptoms begin to improve after 1 month of adequate corticosteroid treatment. Muscle enzymes decrease, erythrocyte sedimentation slows, and urinary creatine and creatinine reverse. At this time, corticosteroids can be reduced. At first, it can be reduced by about 1/4, and then the rate of decrease decreases. If the condition is stable, it can be reduced every 2 to 4 weeks. At the same time, observe the change of the condition closely, and be careful not to repeat. When reducing to 1/2 of the starting dose, the dose should be less and slower each time. Finally, take 0.1 to 0.2 mg / kg of prednisone every day, which needs to be maintained for more than 2 years (usually prednisone 5 to 10 mg / d, which can be taken every other day). If repeated occurrences occur during the withdrawal of corticosteroids, the dose should be increased immediately, or even restored to the initial therapeutic dose.

In the past, the amount of corticosteroids in JDM was higher than that of adults [2 to 3 mg / (kg · d)], but more and more data show that this is not the case. High-dose corticosteroids are not effective for various JDM (including refractory JDM, mainly severe vasculitis), but greatly increase opportunistic infections and other side effects. Patients often die not from the primary disease but from the cortex Side effects of steroids. For example, Tabarki B and others observed 36 cases of JDM treated with 1 mg / (kg · d) prednisone within 13 years. 78% had no recurrence and no dysfunction. Compared with the dose of 2 mg / (kg · d), the efficacy No difference but higher quality of life and fewer side effects.

3. The treatment of insensitivity to corticosteroids or with contraindications to corticosteroids has not been effective for sufficient corticosteroids for more than 1 month, and the original lesion should be added or switched to other drugs in a timely manner; Hypertension, diabetes, peptic ulcer, bone aseptic necrosis, etc. should be the same at the beginning of treatment, which can reduce the amount of corticosteroids by more than half.

(1) Cytotoxic drugs: Are cytotoxic drugs combined with corticosteroids at the beginning of treatment or added after corticosteroid treatment is ineffective or complication, the results have no effective comparison data at present, generally in corticosteroid treatment Cytotoxic drugs should be added only if the symptoms do not improve for more than 1 month. However, JDM with severe symptoms and obvious vasculitis is suitable for early combination, which can improve symptoms and reduce corticosteroid dosage and complications. Commonly used cytotoxic drugs are:

Cyclophosphamide (CTX): Refer to "Systemic Lupus Erythematosus" for usage and dosage. CTX "shock therapy" can be the first choice for interstitial pneumonia and JDM vasculitis; it also has a satisfactory effect on myositis that "resists" corticosteroids.

Methotrexate (MTX): Adults 10 to 25 mg per week, the highest dose can reach 50 mg / week; children 2 mg / kg every 2 weeks, orally. Methotrexate (MTX) is best taken orally, because injection can affect liver function and increase muscle enzymes.

Azathioprine (AZA): 1-2 mg / (kg · d), orally.

The efficacy of the above three commonly used cytotoxic drugs AZA may be better than cyclic amine phosphate (CTX) and methotrexate (MTX), but the strongest inhibitory effect on bone marrow; methotrexate (

Dermatomyositis and polymyositis diet health care

1. What foods are good for dermatomyositis and polymyositis?

Reasonably arrange your diet to ensure adequate vitamin and protein intake. Clinical medicated diet therapy is usually based on tonic benefits, spleen and kidney, and the medicines that can be used as diet include yam, coix seed, cotoneaster, Cordyceps sinensis, angelica, medlar, gelatin, ganoderma lucidum, purple river car and so on.

2. Which foods are best not to eat for dermatomyositis and polymyositis:

Avoid fatty, cold, spicy products, so as not to hurt the spleen and dampness.

Dermatomyositis and polymyositis preventive care

1. Remove possible inducing factors, such as wind and cold, damp heat, and other harmful factors.

2. Strengthen physical exercise, regular life, pay attention to work and rest.

3. Strengthen nutrition and prevent infection.

4. Adjust your emotions and keep your mood happy.

Dermatomyositis and Polymyositis Pathogenesis

The etiology and pathogenesis of DM and PM are unknown, and may be related to the following factors:

1. Infection A variety of infections have been found (bacteria, viruses, protozoa, etc. are related to this disease. JDM is more certain, there are often upper respiratory infections before onset, and the "O" value of anti-streptococcus is increased, so it is considered to be related to bacterial infections A variety of virus-like particles are found in the nucleus of muscle cells, vascular endothelial cells, tissue cells around blood vessels and fibroblasts in the cytoplasm and nucleus, and increased virus antibodies can be detected in the serum of some patients, especially It is a paramyxovirus. However, the transfer of muscle and plasma from patients with virus infection to animals has not caused animal muscle inflammation; it is unique to Jo-1 (histidine-tRNA synthetase) anti-system PM, and the Jo-1 antigen is in the protein The sequence is similar to some viral antigens, and whether there is a "molecular simulation" effect remains to be further studied.

2. Tumors The disease is more likely to be accompanied by malignant tumors, especially DM, and some reports are as high as 43%. Removal of the tumor lesions can make the disease alleviate, and the patient's tumor extract solution is used to perform a positive intradermal test, and the passive metastasis test is also positive. Antibodies against tumors were found in the patient's serum. The tumor tissues have cross-antigenicity with normal human muscle fibers, tendon sheaths, blood vessels, and connective tissues. These normal tissues can also act as antigens and react with anti-tumor antibodies, causing pathological changes in these tissues. However, there is also a contrary view that the incidence of malignant tumors in patients with DM / PM is not significantly higher than that in the normal population.

3. Immunity Although the diseased organs of DM and PM are mainly muscles, so far it is not known what muscle-specific autoantigens are. The following only shows that there are immunological changes in DM / PM.

For example, in animal experiments, experimental allergic myositis (EAM) can be produced after immunizing animals with skeletal muscle antigens and adjuvants. The animal's lymphocytes have cytotoxic effects on skeletal muscle cells in vivo and in vitro. . In patients, it was found that after contacting peripheral blood lymphocytes with skeletal muscle antigen, the lymphocyte conversion rate was significantly increased, and the degree of increase was also positively related to the degree of disease activity, and decreased after treatment with corticosteroids. The expression of MHC-I molecules on the surface of muscle fibers is increased, showing that muscles become target organs of cytotoxic T cells (Tc). Based on T cell receptor gene rearrangement, Tc of CD8, which has a self-harmful function but no inhibitory function in PM but not DM, is selectively cloned for growth. In DM, -transport growth factor is over-expressed in the connective tissue of the myofibrial membrane, and is down-regulated after treatment and myofibrosis and inflammation subsides; the degenerate muscle fibers also express some anti-apoptotic molecules, such as Bcl-2, which resist Apoptosis-mediated cell death. There are also reports of cytokine-induced myositis, such as PM and high titers of anti-dsDNA antibodies after long-term application of -interferon. The above data show that there is a cellular immune abnormality in DM and PM, especially PM.

There are also abnormalities in humoral immunity, manifested in the detection of a variety of autoantibodies (see "Experimental Examinations"), and more types of autoantibodies in patients with other connective tissue disease (CTD). The only autoantigen that has been specifically observed in DM is Mi2, which is a component of histone deacetylase and nuclear chromatin-modifying active complexes present in the nucleus of the cell. -Mi2 plays a role in chromatin rearrangement of tumor metastasis; it is not clear whether DM is likely to be associated with tumors.

Tissue immunohistochemistry was used to detect the infiltration of CD8 cells around the muscle fibers in the diseased muscle tissue of PM, of which Tc: Ts (inhibitory T cells) was 4: 1; while the inflammatory cells in the diseased muscle tissue of DM surrounded the blood vessel infiltration, of which B cells It is much larger than T cells, and CD4 cells predominate in T cells. The walls of diseased muscle capillaries have IgG, IgM and complement deposition, especially JDM. These show the differences in immune pathogenesis between DM and PM, that is, humoral immune mechanisms may be dominant in DM, and cellular immune mechanisms may be dominant in PM.

4. Heredity Although DM / PM has been reported as familial, it is more often nonfamilial. HLA-B7 is increased in myositis of the Japanese nation, HLA-A24 and HLA-B52 of PM are significantly lower than DM, and CW3 is significantly higher than DM; HLA-DRB1 * 08 allele is in all patients with myositis, especially PM and DM increased significantly, while HLA-DQA1 * 0501 and HLA-1DQB1 * 0301 decreased significantly. In white people, HLA-B8 is more common in adult PM and JDM; HLA-DR3 is strongly correlated with anti-Jo-1 antibodies and interstitial pneumonia. It has also been reported that HLA-DQA1 * 0501 is a dangerous gene for JDM. C4 null genes are highly correlated with JDM. There have been new reports in genetics, but satisfactory results have not yet been achieved.

5. Metabolism The abnormal metabolism of collagen is related to the occurrence of DM / PM. If the carboxyterminal propeptide of type procollagen (PICP) in type DM collagen was found to be significantly elevated, the level of PICP was positively correlated with the level of creatine (CK), while the type collagen procollagen aminoterminal propeptide of type procollagen (PINP) was not changed; metalloproteinases-1 (TIMP-1) levels were also significantly increased; changes in serum PCP and TIMP levels may help evaluate whether DM is active With severity.

Changes in mitochondrial biochemical function of skeletal muscle cells may also be related to the occurrence of DM / PM. For example, in a paired study of normal people of the same age and sex with DM patients, the content of skeletal muscle cytochrome C oxidase negative fibers and succinate dehydrogenase highly reactive fibers was significantly increased in DM; and for different enzymes, The oxidation rate of the substrate, the activity of the electron transport chain, and the ATPase activity were not different between DM and normal people. A small number of patients have high titers of anti-mitochondrial antibodies, and mitochondrial damage was found in the muscle tissue of the biopsy.

Dermatomyositis and Polymyositis Disease Diagnosis

1. Identification of skin symptoms

(1) CTD: It is mainly distinguished from lupus erythematosus, mixed connective tissue disease, Sjogren's syndrome, Wegener's granulomatosis (see related chapters), and other types of skin vasculitis.

(2) Polycentric reticular histiocytosis: also known as lipid cutaneous arthritis. Polycentric reticular histiocytosis is characterized by a brownish red or yellow pimples or nodules (2-10mm) that are more common in the hands (especially the dorsal joints) and the face. The pimples can be fused into moss for a long time. This kind of change can be even on the face, like pityriasis fur; symptomatic polyarthritis that can reach joint deformities. Serological examination of the disease has only mild cholesterol elevation and white / globulin inversion.

Others need to be distinguished from seborrheic dermatitis and photosensitive dermatitis.

2. Identification of muscle symptoms

(1) CTD: such as systemic lupus erythematosus, mixed connective tissue disease, systemic scleroderma, Wegener's granulomatosis, etc. (see related chapters), muscle symptoms are only part of its multiple systemic damage.

(2) Inclusion body myositis (IBM): IBM is common in older men, showing distal muscle weakness, slow development, asymmetry of muscle symptoms, abnormal neuroreflexes during physical examination; except for histological examination Characteristic intracellular vacuoles are visible outside the inflammation. These vacuoles contain eosinophils in paraffin sections and alkaline particles in frozen sections. It is difficult to improve symptoms after treatment, but it does not affect life.

(3) Rheumatic polymyalgia: Rheumatic polymyalgia is characterized by generalized body pain and morning stiffness of the shoulders, hips, trunk, and extremities, without muscle weakness and muscle enzyme abnormalities. It usually develops after 50 years of age, with an average age of 70 years. The ratio of female to male was 2: 1, and the laboratory examination showed rapid erythrocyte sedimentation and moderate anemia.

(4) Hyperthyroid myopathy and diabetic myopathy: The former has a more rapid onset, severe systemic symptoms, and muscle or skin symptoms can be similar to PM or DM; the latter has a slow onset and obvious distal muscle symptoms. Endocrinology tests can be distinguished.

(5) Infectious myopathy: Parasitic, viral, and bacterial infections can cause symptoms similar to DM or PM. When the symptoms do not improve after treatment with immunosuppressants such as corticosteroids, they must be considered for infectious myopathy. may. Among them, Toxoplasma gondii (Toxoplasma gondii) and nematode infections are the most common and most confusing.

It also needs to be distinguished from eosinophiliamyalgia syndrome, eosinophilia syndrome, myasthenia gravis, and muscular dystrophy.

Dermatomyositis and polymyositis examination method

Laboratory inspection:

1. Serum creatine creatine kinase (CK), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), alanine aminotransferase (ALT), and aldolase (ALD), etc. are increased during myositis activity, of which CK The sensitivity is the highest, which can be increased in the early stage of the disease, decreased when the disease begins to stabilize, and the clinical symptoms have not improved, and has relative specificity, so it is of great significance for diagnosis, guidance and treatment and prognosis. Because more than 95% of CK comes from skeletal muscle, CK-MM is the main component of CK, so it is not necessary to add isozymes when diagnosing DM / PM; isoenzymes CK-MB can also be increased, but CK-MB Myocardial involvement should be suspected when / total CK> 80ng / U; CK-BB should be measured when smooth muscle involvement is suspected. The degree of elevation of the above enzymes is sometimes consistent with the degree of muscle lesions, and the measured enzyme values decrease after disease control. Because DM / PM can be associated with liver damage, after treatment, if CK decreases and other enzyme changes are not obvious, specific analysis should be performed, and treatment cannot be considered blindly. Among all muscle enzymes, LDH recovery is the slowest, which can obviously improve clinical symptoms, and other laboratory indicators are still higher than normal when they return to normal.

2. Urine creatine, creatinine Under normal circumstances, the content of creatine in the urine within 24 hours is less than 200mg [4mg / (kg · d)]. When muscle disease occurs, muscle cells cannot effectively take creatine from blood and convert it into creatinine, so the amount of creatine in urine increases and creatinine decreases. Physiological creatineuria can occur during development, menstruation, and some elderly people, but rarely exceeds 4mg / (kg ). The abnormality of urine creatine and creatinine can appear before creatinase, so it is meaningful to diagnose and observe the effect of this disease. This change may be insignificant in some patients with chronic myositis and focal myositis.

3. Autoantibodies DM / PM autoantibodies are divided into 3 categories, of which autoantibodies related to the diagnosis of DM / PM have high specificity but poor sensitivity and low detection rate.

(1) Autoantibodies related to DM / PM diagnosis:

Anti-Jo-1 antibody: This antibody is also called PL-1 antibody. Its antigen is histidine tRNA synthetase, which exists in the cytoplasm. It is also an extractable nuclear antigen (ENA) component with a molecular weight of 55kD. The antibody has a high degree of myositis specificity, which is more common in PM. The positive rate of individual reports can reach 45%, and about 5% in DM. The actual detection rate is not so high. JDM and patients with tumors generally do not have this antibody, and non-myositis patients have not found anti-Jo-1 antibody positive, so this antibody can be referred to as the "labeled antibody" of PM. The antibody-positive patients are often associated with interstitial lung disease, and some patients may have lung lesions far more severe than muscle; Jo-1 antibodies may appear before interstitial pneumonia (see "Jo-1 syndrome").

Anti-Mi2 antibody: Mi2 antigen is a nucleoprotein complex that exists in the cytoplasm of the cell. It can be extracted from the calf thymus. The highest positive rates of anti-Mi2 antibodies were reported in 15% to 35% of DM and 5% to 9% of PM patients. Anti-Mi2 antibody-positive patients respond well to treatment and have a good prognosis. Mi-2 antibodies are rare in DM and JDM with tumors.

Anti-PL7 and PL12 antibodies: PL7 is threonyl tRNA synthetase, and PL12 is alanyl tRNA synthetase. Both antigens are present in the cytoplasm and play a role in tRNA assembly of threonine or alanine, respectively. The molecular weight of PL7 is 80 kD, and the molecular weight of PL12 is 100 kD. Anti-PL7, PL12 antibodies are related to interstitial pneumonia and PM, and the positive rate is only about 5%. It has high specificity and poor sensitivity for the diagnosis of interstitial pneumonia and PM.

(2) Autoantibodies related to the diagnosis of DM / PM overlap syndrome:

Anti-PM-Scl antibody: This antibody is also called anti-PM-1 antibody. The PM-Scl antigen is located in the granular part of the nucleolus and consists of at least 10 peptides with a molecular weight of 20-100 kD. Among them, 75kD and 100kD are the polypeptides with the most antigenic activity, and the 100kD polypeptide also has homology in amino acid sequence with serine and threonine protein kinases. Anti-PM-Scl antibodies appear in the overlapping syndrome of PM and scleroderma at most, with a reported positive rate of 24%; it can also appear alone in PM or systemic scleroderma with positive rates of 8% and 2% ~ 5%. Patients with PM-Scl antibody-positive scleroderma are more likely to have skin calcium and arthritis than PM-Scl antibody-negative patients. They have a better prognosis, almost no visceral damage, and a 10-year survival rate of 100%.

Anti-Ku antibody: This antibody is also called anti-p70 / p80 antibody. Ku antigen is a protein that binds to the terminal part of the DNA chain. It is located in the nucleus and nucleoli of interphase cells and consists of 66kD and 86kD proteins. These two proteins form a heterodimer that binds to DNA and may play a role in transcription, DNA replication, and cell proliferation. According to Japanese scholars, the positive rate of anti-Ku antibody in Japanese PM and systemic scleroderma OLS is 26%, and the specificity is 99%, so the "labeled antibody" of Ku anti-system OLS; the antibody-positive OLS Patients have a good prognosis. But other nations are not. For example, American scholars reported that anti-Ku antibodies appeared in SLE at most, with a positive rate of 19%; systemic scleroderma was 14%; and OLS was negative; whether the antibody was positive or not with SIE or scleroderma Has no clinical symptoms. About 89% of anti-Ku antibodies are related to HLA-DQw1, and most of these antibodies appear simultaneously with anti-Sm antibodies. Anti-ku antibodies also occur in 23% of patients with primary pulmonary hypertension. Primary pulmonary hypertension with anti-Ku antibodies is prone to Raynaud's phenomenon, antinuclear antibodies, and pulmonary vasculitis.

Anti-SS-A (Ro) and SS-R (La) antibodies (see "Sjogren's syndrome"): About 8% of DM / PM patients may have anti-SS-A or SS-B antibodies, mostly overlapping SS or SLE.

(3) Autoantibodies not related to DM / PM diagnosis:

Anti-muscle component antibodies: Anti-muscle component antibodies include antibodies such as myoglobin, myosin, troponin, and tropomyosin. Various anti-muscle component antibodies are more likely to appear in DM / PM serum. For example, the anti-myoglobin antibody positive rate in PM can reach 71%, and the anti-myosin antibody positive rate can reach 90%. Diseases also have such antibodies and lack specificity.

Rheumatoid factor (RF): RF can also be positive, but the titer is not high. RF-positive individuals are prone to morning stiffness.

Antinuclear antibodies: Immunofluorescent antinuclear antibodies (IFANA) and anti-RNP antibodies (see "Lupus erythematosus" section) can be detected in a small number (about 15%) of DM / PM patients.

4. Electromyography More than 70% of patients have abnormal EMG, showing myogenic changes. Because the degree of muscle involvement in each group is different, generally more than 3 muscles of the upper and lower limbs should be detected at the same time. The paraspinal muscle can be examined when the electromyogram of the extremities is normal. EMG can only be used as an auxiliary diagnosis, especially to help distinguish it from neurogenic myasthenia. For example, neuromyositis exhibits a longer sensory and motor nerve conduction time.

5. Imaging Many foreign scholars try

Other auxiliary checks:

Histopathology: Pathological changes of muscles are of great significance for diagnosis. Biopsy should select muscles with obvious symptoms, usually the proximal muscles are deltoid or quadriceps. Perivascular and interstitial inflammatory infiltration, mostly lymphocytes, macrophages and plasma cells. Muscle fibers swell, horizontal stripes disappear, cytoplasm becomes transparent, and degeneration of varying degrees. In severe cases, muscle fibers are broken and swallowed. The late muscle fiber structure disappears and is replaced by connective tissue. Some cases have obvious changes in vasculitis, edema and necrosis of the vessel wall, thickening of the intima, narrowing of the lumen and even embolism.

The histological changes of the skin are not specific in DM, and the clinical manifestations have reference significance for diagnosis.

Dermatomyositis and Polymyositis Complications

The majority of amyopathic dermatomyositis (ADM) is associated with malignancies. Lungs and other organs are severely damaged, and those with other CTDs are less likely to have tumors. A few patients have typical myositis clinically, but muscle biopsy fails to find typical pathological changes, and even CK does not increase. Such patients may be more likely to have tumors. The incidence of malignant tumors in patients with myositis is low. The incidence of cardiomyopathy is high in patients with scleroderma.

Dermatomyositis and Polymyositis Prognosis

1. Patients with cutaneous vasculitis are likely to have systemic vasculitis at the same time, often with severe symptoms and poor prognosis when not treated properly; those with skin calcium deposits often have important organ damage and have a good prognosis

2. Acute process, severe dysphagia, high fever with leukocytosis, gastrointestinal ulcers, and severe vasculitis. Those who are not sensitive to corticosteroid treatment need to add cytotoxic drugs, and the prognosis is poor.

3. Corticosteroid treatment is not sensitive and requires the addition of cytotoxic drugs, the prognosis is poor. However, those with chronic organ damage, vasculitis, and other organ damage without or mild skin calcification are sensitive to corticosteroid treatment and have a good prognosis.

4. Mucin deposition is prone to occur in middle-aged and elderly female patients, and may be the first symptom of DM; blisters or bullae have a poor prognosis. Very few patients have heart failure and severe arrhythmia due to myocardial disease, the prognosis is poor, and most of these patients have systemic scleroderma.

5. PM-Scl antibody-positive scleroderma patients are more likely to have skin calcium and arthritis than PM-Scl antibody-negative patients, with a better prognosis, almost no visceral damage, and a 10-year survival rate of 100%.

6. Respiratory system Common lung diseases are: interstitial pneumonia (ILD), the incidence is> 40%; alveolitis (> 30%) and ventilation disorders caused by bronchial pneumonia (about 20%). It develops slowly, may have different degrees of dyspnea, and is prone to secondary infection. According to foreign statistics, the incidence of DM / PM in the above three lung diseases is 40%, and the mortality rate is 27%.

Dermatomyositis and Polymyositis Pathogenesis

The pathogenesis is unknown, and may be related to the following factors:

1. Infection Some people think that it is related to allergic reactions after bacterial infection. In the nucleus of muscle cells, a variety of virus-like particles were found in the cytoplasm and nucleus of vascular endothelial cells, tissue cells and fibroblasts around blood vessels, and increased viral antibodies, especially paramyxoviruses, were detected in the serum of some patients.

2. Tumor The disease is more likely to be accompanied by a malignant tumor. It has been reported as high as 43%. Removal of the tumor lesions can make the disease alleviate, and the patient's tumor extract solution is used to perform a positive intradermal test, and the passive metastasis test is also positive.

3. Immune In patients, it was found that after contacting peripheral blood lymphocytes with skeletal muscle antigens, the lymphocyte conversion rate was significantly increased, and the degree of increase was also positively related to the degree of disease activity, and decreased after treatment with corticosteroids.

4. Genetics HLA-DQA1 * 0501 has been reported as a dangerous gene for JDM; C4 null genes are highly related to JDM.

5. Metabolism The abnormal metabolism of collagen is related to the occurrence of DM / PM.