Dermatomyositis and Polymyositis

Introduction to dermatomyositis and polymyositis Dermatomyositis (DM) and polymyositis (PM) are currently considered to be in the category of autoimmune diseases. DM manifests as diffuse inflammation of the skin and muscles, erythema on the skin, edema, muscle weakness, pain and swelling, may be associated with joint pain and multiple organ damage such as the lungs and myocardium; PM has no skin damage. basic knowledge The proportion of illness: 0.014% Susceptible people: no specific population Mode of infection: non-infectious Complications: scleroderma cardiomyopathy

Dermatomyositis and the cause of polymyositis

(1) Causes of the disease

The etiology and pathogenesis of DM and PM are not known and may be related to the following factors:

Infection (37%):

A variety of infections have been found (bacteria, viruses, protozoa, etc. are related to this disease, more definitely JDM, there is often upper respiratory tract infection before the onset of the disease, anti-streptococcus "O" value is elevated, it is considered to be allergic to bacterial infection Related, in the nucleus of the myocytes, vascular endothelial cells, perivascular tissue cells and fibroblast cytoplasm and nucleus found a variety of virus-like particles, in some patients serum can also detect increased viral antibodies, especially para-mucus The virus, but transferring the muscles and plasma of these infected patients to the animals failed to cause inflammation in the animal; Jo-1 (histidyl-tRNA synthetase) is unique to PM, and the Jo-1 antigen is in the protein sequence. Some viral antigens are similar in appearance, and whether there is a "molecular simulation" effect remains to be further studied.

Tumor (21%):

The disease is associated with a higher incidence of malignant tumors, especially DM, and some reported up to 43%. Resection of tumor lesions can alleviate the disease. The patient's tumor solution is positive for intradermal test, and the passive transfer test is also Positive, the antibody is found in the serum of the patient. The tumor tissue and the normal muscle fibers, tendon sheath, blood vessels and connective tissue of the human body have cross-antigenicity. These normal tissues can also react with anti-tumor antibodies as antigens, resulting in lesions of these tissues. However, there is also a contrary view that the incidence of malignant tumors in DM/PM patients is not significantly higher than that in the normal population.

Immunization (17%):

Although the diseased organs of DM and PM are mainly muscles, it is not known so far that it is a muscle-specific autoantigen. The following can only show that there is an immunological change in DM/PM.

For example, in animal experiments, experimental allergic myositis (EAM) can be produced by immunizing animals with skeletal muscle antigens and adjuvants. The lymphocytes of this animal produce cytotoxic effects on skeletal muscle cells both in vivo and in vitro. After the patient's peripheral blood lymphocytes were exposed to skeletal muscle antigen, the lymphocyte transformation rate was significantly increased, and the degree of elevation was also positively correlated with the degree of disease activity, and decreased after treatment with corticosteroids. MHC on the surface of muscle fibers. Increased expression of class I molecules, showing that muscles become target organs of cytotoxic T cells (Tc), based on T cell receptor gene rearrangement, Tc of CD8 with self-injury function and no inhibitory function in PM but not DM Selectively clonal growth, in DM, -transport growth factor is overexpressed in the connective tissue of the fascia, and is down-regulated after treatment and muscle fiber degeneration and inflammation subsided; degenerated muscle fibers also express some anti-apoptotic molecules, Such as Bcl-2, resistance to apoptosis-mediated cell death, as well as cytokine-induced myositis, such as PM after long-term use of -interferon High titers of anti-dsDNA antibodies, particularly the above data show that the PM cellular immune abnormalities in DM and PM.

There are also abnormalities in humoral immunity, which can be detected as a variety of autoantibodies (see "Experimental Examination"). There are more types of autoantibodies in patients with other connective tissue diseases (CTD). Currently only observed in DM is specific. The sexual autoantigen is Mi2, which is a component of histone deacetylase and nuclear chromatin-modified active complex present in the nucleus. It is reported that the chromatin of -Mi2 in tumor metastasis is heavy. It plays a role in platoon; it is not clear whether DM is associated with tumors.

Using tissue immunochemistry, it was found that CD8 cells in the muscle tissue of PM were infiltrated around muscle fibers, and Tc:Ts (inhibitory T cells) was 4:1; while inflammatory cells in DM lesions infiltrated around blood vessels, and the number of B cells It is much larger than T cells, and CD4 cells are dominant in T cells; IgG, IgM and complement deposition, especially JDM, in the capillary wall of diseased muscles, which shows the difference in immune pathogenesis between DM and PM, ie DM The humoral immune mechanism may predominate, and the cellular immune mechanism may predominate in PM.

Genetic (15%):

Although there is a report of familial DM/PM, it is more non-familial. In the Japanese myositis, HLA-B7 is increased, and PM's HLA-A24 and HLA-B52 are significantly lower than DM. CW3 was significantly higher than DM; HLA-DRB1*08 allele was significantly elevated in all myositis patients, especially PM and DM, while HLA-DQA1*0501 and HLA-1DQB1*0301 were significantly lower in Caucasians. HLA-B8 is more common in adult PM and JDM; HLA-DR3 is strongly correlated with anti-Jo-1 antibody and interstitial pneumonia. HLA-DQA1*0501 is also reported as a risk gene for JDM, C4 null gene and JDM is highly correlated, and there are new reports in genetics, but there have been no satisfactory results.

Metabolism (9%):

Abnormal collagen metabolism is related to the occurrence of DM/PM. If the carboxyterminal propeptide of type I procollagen (PICP) is significantly increased in DM serum, the PICP level is positively correlated with creatine (CK) level. However, the amino terminal propeptide of type I procollagen (PINP) showed no change; the level of metalloproteinases-1 (TIMP-1) was also significantly increased; serum PICP and TIMP levels were Changes may help to assess the activity and severity of DM conditions.

Changes in mitochondrial biochemical function in skeletal muscle cells may also be associated with the development of DM/PM. For example, skeletal muscle cytochrome c oxidase-negative fibers and succinic acid were observed in a paired study of normal age and gender of the same age and gender. The content of hydrogenase-reactive fiber was significantly increased in DM; while the oxidation rate of different enzyme substrates and the activity of electron transport chain and ATPase were not different between DM and normal people, and a small number of patients had high titer in serum. Anti-mitochondrial antibodies, mitochondrial damage was found in the muscle tissue of the biopsy.

(two) pathogenesis

The pathogenesis is not yet clear and may be related to the following factors:

1. Infection is thought to be related to allergic reactions after bacterial infection. In the nucleus of the muscle cells, vascular endothelial cells, perivascular tissue cells and fibroblasts are found in the cytoplasm and nucleus of various virus-like particles. Increased viral antibodies, especially paramyxoviruses, were detected.

2. The incidence of tumors associated with malignant tumors is high, as reported by up to 43%. Resection of tumor lesions can alleviate the disease. The patient's tumor solution is positive for intradermal test, and the passive transfer test is also positive.

3. Immunization In patients, it was found that the peripheral blood lymphocytes were exposed to skeletal muscle antigen, and the lymphocyte transformation rate was significantly increased. The degree of elevation was also positively correlated with the degree of disease activity and decreased after treatment with corticosteroids.

4. Genetics reported that HLA-DQA1*0501 is a dangerous gene for JDM; C4 null gene is highly correlated with JDM.

5. Metabolic collagen metabolism abnormalities are related to the occurrence of DM/PM.

Dermatomyositis and prevention of polymyositis

1. Remove possible incentives, such as cold, damp heat and other adverse factors on the human body.

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 complications of polymyositis Complications scleroderma cardiomyopathy

Most of myopathic dermatomyositis (ADM) is associated with malignant tumors. The lungs and other organs are severely damaged. The possibility of tumors associated with other CTD patients is small. A few patients have typical myositis clinically. However, muscle biopsy failed to find typical pathological changes, and even CK did not increase. Such patients may have larger tumors. The incidence of malignant tumors in patients with myositis is low, and myocardial lesions in patients with scleroderma The incidence is high.

Dermatomyositis and multiple myotitis symptoms common symptoms dyspnea constipation hair inflammatory cells infiltration respiratory failure mitral valve prolapse myalgia skin heterochromia double upper eyelid edema... rheumatoid arthritis

Skin and muscle are the main symptoms of the two groups. The skin often precedes the muscles for several weeks to several years. It can also have myositis or muscle and skin at the same time. The skin and muscle symptoms are often not parallel, but one is very heavy and the other is Lighter, the first symptom of the individual case may not be the skin or muscles, but the heart, lungs or pleura, manifested as pericardial tamponade, pulmonary fibrosis or pleurisy.

1. Skin symptoms The typical skin lesions are edematous purple-red spots on the upper eyelids, which spread to the periorbital, gradually expanding to the face, neck, and upper chest V-shaped areas, limbs elbow and knees, especially metacarpophalangeal joints and finger joints. Purple-red papules appear on the extensor side, with telangiectasia, hypopigmentation, overlying small scales, called Gottron (Gordon) sign or Grottron papules, edematous purplish red spots on the upper eyelid and Gottron sign are important basis for the diagnosis of DM. Especially the former, the earliest, is very meaningful for early diagnosis, most patients have no pain, itching and other skin lesions.

Other skin damage types of DM include heterochromia, erythroderma, cutaneous vasculitis, urticaria, calcareous, etc., and the possibility of cutaneous heterochromia with malignant tumors increases; cutaneous vasculitis, skin calcification It occurs mostly in JDM. Patients with cutaneous vasculitis are prone to systemic vasculitis at the same time. They often have severe symptoms. The prognosis is poor when the treatment is not proper. People with skin calcification often have important organ damage and good prognosis, but also have extensive abdominal wall. Calcium deposition caused by acute abdomen and intra-abdominal hemorrhage, rarely occurred in the type of lesions with plaque skin mucin deposition and blister or bullous damage, mucin deposition is likely to occur in middle-aged and elderly women, can be DM First symptoms; vesicles or bullae have a poor prognosis.

2. Muscle symptoms involve the striated muscle, but the involvement of skeletal muscle is much more common than that of the myocardium; the smooth muscle is rarely affected, and the proximal muscles of the extremities are most vulnerable, such as the deltoid muscle and the quadriceps muscle, and the multiple symmetric disease, the diseased muscles are weak. And pain and other symptoms, and the corresponding dyskinesia, the upper limbs are difficult to lift, the lower limbs can not lift and squat can not stand up; the heavier ones are difficult to lift, can not turn over, showing the neck and trunk muscles involved; serious The limbs can't move in the bed or can only move a few centimeters, or even see a slight muscle contraction. When the esophagus and throat muscles are involved, there are difficulty in swallowing, eating cough, changing pronunciation, etc., and respiratory muscle involvement may cause shortness of breath. Difficulty breathing, eye muscle involvement and diplopia, a small number of patients can have no muscle pain and only manifest as muscle weakness.

3. Other system symptoms

(1) Digestive system: gastrointestinal symptoms are most common in systemic damage, manifested as abdominal distension, loss of appetite, digestion and malabsorption, constipation or diarrhea, nearly one-third of patients have difficulty swallowing, mainly difficulty in swallowing solid food; Esophageal barium meal in the supine position, 2 / 3 patients can be found abnormal, such as esophageal dilatation, poor peristalsis, contrast agent through slow and piriform sputum retention, JDM can also cause intestinal necrosis due to vasculitis, stomach Intestinal ulcers and hemorrhage, liver function abnormalities are more common in disease activities, individual patients may have gallbladder sclerosis, cholestatic hepatitis, at this time can detect anti-mitochondrial antibodies.

(2) Respiratory system: common lung lesions are: interstitial pneumonia (ILD), incidence >40%; alveolitis (>30%) and bronchial pneumonia caused by ventilatory disorders (about 20%), mostly slow Development, there may be varying degrees of dyspnea, easy to secondary infection, according to foreign statistics, the above three kinds of lung lesions in the DM / PM incidence rate of 40%, mortality was 27%; and considered high levels of serum aspartate aminotransferase (AST) and ferritin, anti-Jo-1 antibody-positive and characteristic microangiopathy are helpful in determining lung lesions and estimating prognosis. Non-invasive early examination of lung lesions can be performed by high-resolution CT (HRCT) And pulmonary function tests, more patients with asymptomatic pulmonary fibrosis than X-ray films, the most sensitive to the function of carbon monoxide diffusion (DLCO) in lung function tests, can detect early patients with no change in imaging, especially Alveolitis, HRCT can not be detected.

A few patients with pulmonary interstitial lesions appear in acute form, can occur at any stage, manifested as acute fever, difficulty breathing, cyanosis, dry cough, but the symptoms of muscle weakness can not be obvious, respiratory failure occurs quickly, the prognosis is poor, such patients serum Middle creatine (CK) is often at a normal level, while AST is significantly elevated, CK to AST ratio is decreased; peripheral blood leukopenia, absolute lymphocyte count is low; lymphocytes in bronchial lavage fluid are significantly increased; patients with throat muscle involvement Aspiration pneumonia can also occur; pleurisy can sometimes occur; individual pneumothorax, mediastinal gas and even extensive subcutaneous emphysema can also occur.

(3) Heart: heart disease is more, about 50% can be found abnormal, but most of them are mild, only ECG shows ST-T changes, other arrhythmia and different degrees of conduction block, mitral valve prolapse More common, very few patients with heart failure due to myocardial disease, severe arrhythmia, this time the prognosis is poor, such patients with systemic scleroderma, most patients are sensitive to corticosteroid treatment, ECG abnormalities can be Muscle/skin symptoms improved and recovered.

(4) Kidney: Kidney lesions are mild and rare (except for other CTD), and may have a small amount of proteinuria, tubular urine and hematuria.

4. Special types

(1) JDM: Children's PM is rare, mostly JDM. The age range of JDM is 4 to 15 years old. According to Pachman LMZ's statistics of 79 cases of JDM in 1998, the symptoms of patients are: skin erythema 100%. Distal muscle weakness 100%, muscle pain 73%, fever 65%, dysphagia 35%, hoarseness 34%, abdominal pain 29%, joint pain 28%, skin calcium deposition 18%, melena 10%; laboratory examination 10% normal muscle enzyme, 8% normal electromyogram, 10% muscle biopsy normal; from symptom onset to diagnosis on average 2 months, unlike adult DM/PM, JDM is more related to infection, clinical manifestations are more urgent Severe vasculitis and easy to have calcium calcification, including acute dysphagia, severe dysphagia, high fever with leukocytosis, gastrointestinal ulcers, severe vasculitis are not sensitive to corticosteroid therapy, need to add cytotoxic drugs, The prognosis is poor, and the chronic disease, vascular inflammation and other organ damage are not or light, and those with calcified skin are sensitive to corticosteroid treatment, and the prognosis is good.

(2) Overlapping syndrome (OLS): DM or PM can overlap with other CTD, often with systemic scleroderma (common type of extremity), systemic lupus erythematosus, rheumatoid arthritis and Sjogren's syndrome , polyarteritis, etc., especially overlap with scleroderma, so Raynaud's phenomenon (RP) often appears before muscle symptoms, OLS is two diseases in the same patient, so the diagnosis of OLS should be strictly in accordance with their respective diagnostic criteria, Such as scleroderma may have muscle weakness, muscle biopsy can be seen muscle atrophy and fibrosis, but no inflammatory cell infiltration, serum muscle enzymes are normal; SLE muscle symptoms can be quite obvious, and muscle biopsy and myositis similar, but the two The type of autoantibodies is different. The incidence of malignant tumors in patients with myositis is low, and the incidence of myocardial lesions is high in patients with scleroderma.

(3) With tumor: adult DM / PM combined tumors have a high incidence, especially DM, more than 1 times more than PM, especially in patients >50 years old, tumors can occur simultaneously with DM, but more common is the appearance of skin Muscle symptoms, only a few months or even years after the discovery of malignant tumors, so the treatment is not good and the middle-aged DM should be systematically examined to rule out the tumor, on the contrary, the lungs and other organs are seriously damaged, combined with other CTD The possibility of tumor involvement is small, a small number of patients have typical myositis in the clinic, but the muscle biopsy fails to find typical pathological changes, and even CK does not increase. Such patients may have larger tumors, and which tumors The easiest to accompany DM/PM, different countries, regions and different ethnic groups.

Examination of dermatomyositis and polymyositis

1. Serum muscle enzymes creatine kinase (CK), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), alanine aminotransferase (ALT), and aldolase (ALD) are elevated during myositis activity, of which CK It has the highest sensitivity, can be elevated at the beginning of the disease, the disease begins to stabilize, the clinical symptoms have not been improved, and it has relative specificity. Therefore, it is of great significance for diagnosis, guiding treatment and estimating prognosis, because more than 95% of CK comes from Skeletal muscle, CK-MM is the most important component of CK, so it is not necessary to add isozyme in the diagnosis of DM/PM; isozyme CK-MB can also be increased, but CK-MB/total CK>80ng/U It should be suspected that myocardial involvement; CK-BB is suspected when smooth muscle is involved, and the degree of increase of various enzymes is sometimes consistent with the degree of muscle lesions. The enzyme measurement value decreases after the disease is controlled. Because DM/PM may be associated with liver damage, After treatment, if CK is decreased and other enzymes are not obvious, it must be analyzed. It is not considered that the treatment is ineffective. The recovery of LDH is the slowest in all muscle enzymes, but the clinical symptoms are obviously improved, and other laboratory indicators are still higher than normal. Normal value.

2. Creatine creatinine, creatinine under normal conditions 24h urine creatine content less than 200mg [4mg / (kg · d)], when muscle disease, muscle cells can not effectively take creatine from the blood and convert it to creatinine, Therefore, the amount of creatine in the urine is increased, and creatinine is reduced. During the developmental period, physiological creatine can occur in menstruation and some elderly people, but rarely exceeds 4 mg/(kg·d), and creatinine does not decrease (urine creatine/ Creatine + creatinine 0.1, which is helpful for diagnosis), abnormalities of creatinine and creatinine can occur before muscle enzymes, so it is meaningful to diagnose and treat the disease in some cases of chronic myositis and focal muscle. This change may not be apparent in patients with inflammation.

3. Autoantibodies DM/PM autoantibodies are classified into three categories. Among them, autoantibodies related to DM/PM diagnosis have high specificity but poor sensitivity and low detection rate.

(1) Autoantibodies related to DM/PM diagnosis:

1 anti-Jo-1 antibody: the antibody is also called PL-1 antibody, the antigen is histidyl tRNA synthetase, exists in the cytoplasm, is also one of the extractable nuclear antigen (ENA) components, molecular weight 55kD, Antibodies have a high degree of myositis specificity, more common in PM, the individual reported positive rate of up to 45%, about 5% in DM, the actual detection rate is not so high, JDM and patients with tumors generally do not have this antibody, non-muscle Inflammatory patients have not been found to be positive for anti-Jo-1 antibodies, so the antibody can be called a "labeled antibody" of PM. The antibody-positive patients are often associated with interstitial lung disease, and some patients have lung lesions that are much more important than muscle; Jo -1 antibodies can occur prior to interstitial pneumonia (see "Jo-1 syndrome").

2 anti-Mi2 antibody: Mi2 antigen is a nuclear protein complex present in the nucleus of the nucleus. It can be extracted from the calf thymus. The protein has a molecular weight of 218kD and is encoded by the 12th chromosome. Its structure belongs to the helicase family and the anti-Mi2 antibody is the highest. The positive rate was reported to be 15% to 35% of DM and 5% to 9% of PM patients. Anti-Mi2 antibody-positive patients responded well to treatment with good prognosis, and tumor-derived DM and JDM rare Mi-2 antibodies.

3 anti-PL7, PL12 antibodies: PL7 is threonyl tRNA synthetase, PL12 is alanyl tRNA synthetase, both of these antigens are present in the cytoplasm, which play a role in the assembly of thionine or alanine in tRNA, respectively. The molecular weight of PL7 is 80kD, the molecular weight of PL12 is 100kD, and the anti-PL7, PL12 antibody is associated with interstitial pneumonia and PM. The positive rate is only about 5%. It has high specificity for the diagnosis of interstitial pneumonia and PM, and its sensitivity is very high. difference.

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

1 anti-PM-Scl antibody: The antibody is also called anti-PM-1 antibody. The PM-Scl antigen is located in the granule part of the nucleolus and consists of at least 10 polypeptides with a molecular weight of 20-100 kD, of which 75kD and 100kD are the most antigen-active. Polypeptide, 100kD polypeptide also has homology with amino acid sequence of serine and threonine protein kinase, anti-PM-Scl antibody appears at most overlap syndrome of PM and scleroderma, and the reported positive rate is up to 24%; It can also occur alone in PM or systemic scleroderma, with positive rates of 8% and 2% to 5%, respectively. PM-Scl antibody-positive scleroderma patients have a higher likelihood of skin calcification and arthritis than PM- Scl antibody-negative patients are much larger, with a good prognosis, almost no visceral damage, and a 10-year survival rate of 100%.

2 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 strand. It is located in the nucleus and nucleolus of interphase cells and is composed of two proteins, 66kD and 86kD. These two proteins constitute a heterodimer that binds to DNA and may play a role in transcription, DNA replication and cell proliferation. According to Japanese scholars, anti-Ku antibodies are found in Japanese PM and systemic scleroderma OLS. The positive rate is 26%, and the specificity is 99%. Therefore, the Ku-anti-system OLS "labeled antibody"; the antibody-positive OLS patients have a good prognosis, but other ethnic groups are not. As American scholars report, anti-Ku antibodies appear at most in SLE. Among them, the positive rate was 19%; systemic scleroderma was 14%; and OLS was negative; whether the antibody was positive or not was not related to the clinical symptoms of SIE or scleroderma, about 89% of anti-Ku antibody and HLA-DQw1, Relatedly, the antibody mostly appeared together with anti-Sm antibody, anti-ku antibody also appeared in 23% of patients with primary pulmonary hypertension, anti-Ku antibody-positive primary pulmonary hypertension is prone to Raynaud, anti-nuclear antibody positive and lung Vasculitis.

3 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:

1 anti-muscle component antibody: anti-muscle component antibody including anti-myoglobin, myosin, troponin, tropomyosin and other antibodies, various anti-muscle component antibodies appear in DM / PM serum is more likely, such as The anti-myoglobin antibody has a positive rate of 71% in PM and an anti-myosin antibody-positive rate of 90%, but many other diseases also have such antibodies and lack specificity.

2 types of rheumatoid factor (RF): RF can also be positive, but the titer is not high, RF positive people are prone to morning stiffness.

3 anti-nuclear antibodies: immunofluorescent anti-nuclear antibodies (IFANA) and anti-RNP antibodies (see section "Luo lupus") can be detected in a small number (about 15%) of DM/PM patients.

4. More than 70% of patients with EMG have abnormal EMG, which is myogenic. Because of the different degrees of muscle involvement in each group, it is generally necessary to detect more than 3 muscles in the lower limbs. When the EMG of the limbs is normal. The paravertebral muscle can be examined. The EMG can only be used as an auxiliary diagnosis, especially to help distinguish the neurogenic muscle weakness. For example, the myoelectricity of neuromyositis is prolonged by the sensory and motor nerve conduction time.

5. Imaging studies Many foreign scholars have tried to diagnose muscle lesions by magnetic resonance imaging (MRI), ultrasound images and isotope methods. MRI definitely helps the positioning of muscle biopsy and the therapeutic effect from the longitudinal direction.

6. Others have increased erythrocyte sedimentation rate during disease activities. They can be used as indicators for judging whether the disease is active and observing the curative effect. Peripheral blood may have mild anemia and elevated white blood cells, especially JDM leukocytes, which are mainly neutrophils.

Histopathology: The pathological changes of muscles are important for diagnosis. Biopsy should select muscles with obvious symptoms. Generally, the proximal muscles are deltoid or quadriceps, and perivascular and interstitial inflammatory infiltration, mostly lymphocytes. Macrophages and plasma cells, muscle fiber swelling, transverse stripes disappear, cytoplasm is transparent, varying degrees of degeneration, severe muscle fiber breaks, phagocytosis, late muscle fiber structure disappears, replaced by connective tissue, some cases have obvious vasculitis changes The vascular wall is edematous and necrotic, the intima is thickened, the lumen is narrow or even embolized.

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

Diagnosis and differentiation of dermatomyositis and polymyositis

Diagnostic criteria

1. The diagnosis of PM is mainly based on muscle weakness and pain, elevated serum muscle enzymes, muscle biopsy and electromyography; DM diagnosis plus skin damage.

2. Diagnostic criteria for DM and PM

(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 rash of the skin, including upper eyelid purple spot and periorbital edematous purplish 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

1. Identification of skin symptoms

(1) CTD: mainly needs to be differentiated from lupus erythematosus, mixed connective tissue disease and Sjogren's syndrome, Wegener's granulomatosis (see related section) and other types of cutaneous vasculitis.

(2) multi-center reticular cell hyperplasia: also known as lipid-like skin arthritis, multi-center reticular cell hyperplasia is characterized by a good appearance in the hands (especially refers to the dorsal joints) and the texture of the face is hard Brownish red or yellow papules or nodules (2~10mm), the papules can be fused with mossy changes, and even on the face can be like red pityriasis; symmetry polyarthritis of joint deformity, the disease Serological tests only had mild elevated cholesterol and white/globulin inversion.

Others need to be differentiated 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 section), muscle symptoms are only part of its multi-system damage.

(2) inclusion body myositis (IBM): IBM is common in older men, manifested as distal muscle weakness, slow development, muscle asymmetry, neurological abnormalities during physical examination; histological examination Characteristic intracellular vacuoles can be seen outside the inflammation. This vacuole contains eosinophils in the paraffin section, while the frozen section contains alkaline particles. The symptoms are difficult to improve after treatment, but do not affect life.

(3) rheumatic polymyalgia: rheumatic polymyalgia is characterized by generalized pain and shoulder, hip, trunk and proximal limbs near morning stiffness, no muscle weakness and muscle enzyme abnormalities; more than 50 years old, the average age is 70 years old The ratio of female to male is 2:1. The laboratory tests for increased erythrocyte sedimentation rate and moderate anemia.

(4) Hyperthyroidism and diabetic myopathy: The former is more acute, the systemic symptoms are heavier, and the muscle or skin symptoms are similar to PM or DM; the latter is slowly onset, the distal muscle symptoms are obvious, and the endocrine examination Can be distinguished.

(5) Infectious myopathy: parasites, viruses, and bacterial infections can cause symptoms similar to DM or PM. After treatment with immunosuppressive agents such as corticosteroids, symptoms must be improved without regard to the presence or absence of infectious myopathy. Possibly, the toxoplasma (toxoplasma) and nematode infections are the most common and most confusing.

It also needs to be differentiated from eosinophilia myalgia syndrome, eosinophilia syndrome, myasthenia gravis, muscular dystrophy.

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