Dermatomyositis

Introduction to dermatomyositis Dermatomyositis (DM), also known as poikilodermatomyositis, is one of the autoimmune connective tissue diseases. It is a non-suppurative inflammation mainly involving striated muscle and lymphocyte infiltration. Lesions, with or without multiple skin lesions, can also be associated with various visceral lesions. Polymyositis (PM) refers to the disease in this group without skin damage. basic knowledge The proportion of illness: 0.06% Susceptible people: no special people Mode of infection: non-infectious Complications: joint pain, heart failure, pleurisy, interstitial pneumonia

Dermatomyositis etiology

The exact cause is not clear enough. It may be a viral infection, an abnormal recognition of the body's immune abnormalities and vascular lesions. The three may also be related to each other. For example, lentivirus infection of striated muscle fibers may cause changes in muscle fiber antigenicity, which is mistaken by the immune system. It is considered to be "existing", which causes vasculitis to occur.

1. Immunological research In view of the increase in serum immunoglobulin, muscle biopsy specimens showed IgG, IgM and C3 in the tiny blood vessels and C56-C9 deposition in the complement membrane attack complex. The degree of deposition seems to be related to disease activity, Arahata and Engel. It was confirmed that there was a significant increase in B cells in inflammatory lesions of DM, suggesting an increase in local humoral effects, but some scholars believe that the deposition of these antibodies is a consequence of muscle damage rather than its cause, and some scholars have found blood lymphocytes around patients. After the addition of striated muscle antigen, the conversion rate and macrophage migration inhibition test were high, and it was positively correlated with its activity. After glucocorticoid reduction, the peripheral blood lymphocytes of patients were cytotoxic to myoblasts in vitro. The role of its damage may be the release of lymphotoxin or direct adhesion and invasion of muscle fibers.

2, sensory theory In recent years, some scholars have observed the muscle and skin lesions of patients with electron microscopy, found that muscle cells, vascular endothelial cells, perivascular tissue cells and fibroblasts and nuclear membranes have similar mucinous or paramyxoviruses. The granules, recently reported that Coxackie A9 virus was isolated from the diseased muscles of 11-year-old girls, so the infection theory was proposed. However, in animal experiments, it has not been able to inject muscles of patients, plasma and cause muscle inflammation from patients. Antiviral antibodies cannot be detected in the blood. In children with dermatomyositis, there is often a history of upper respiratory tract infection before the onset, anti-streptococcal "O" value increased, antibiotics combined with corticosteroid treatment can be effective, proposed infection allergy theory.

3. Vascular lesions Vascular lesions have been described especially in children with DM. Any diffuse vascular lesion can produce striated muscle ischemia, causing necrosis of individual fibers and infarct areas of muscles. There are capillaries in DM/PM special children. Evidence of endothelial cell damage and thrombosis of blood vessels, and the deposition of immune complexes in intramuscular blood vessels, as well as thickening of the capillary basement membrane, especially in the perisome region of the muscle bundle.

Dermatomyositis prevention

1. Try to avoid direct sunlight (mainly ultraviolet rays), wear hats, gloves, long-sleeved clothes or umbrellas when going out.

2, no cosmetics, hair dyes.

3. Avoid contact with pesticides and certain decorative materials.

4. Women of childbearing age should try their best to avoid pregnancy and abortion when their condition is not very stable. Fertility should be under the guidance of a physician.

Dermatomyositis complications Complications, joint pain, heart failure, pleurisy, interstitial pneumonia

There may be joint pain, deformity and movement of the elbow, knee and shoulder joints. Most of the fibers secondary to adjacent muscle lesions are caused by contracture. Cardiac involvement cases have abnormal cardiac function, tachycardia or slowness, heart enlargement, myocardial damage. Atrial fibrillation and heart failure, may also have pleurisy, interstitial pneumonia, or retinal choroiditis, subarachnoid hemorrhage.

Symptoms of dermabrasion Symptoms Common symptoms Anti-Jo-1 antibody-positive pruritus papule pigmentation photoallergic pigmentation loss scales

It can occur at any age, with a slight majority of women. Some cases have symptoms before the onset, such as irregular fever, Raynaud's phenomenon, joint pain, headache, fatigue and fatigue. Most of the cases are slow onset, and a few are acute or Subacute onset, muscle and skin are the two main symptoms of the disease. Skin lesions often precede the onset of muscle for several weeks to several years. A few have first myopathy, followed by skin lesions, and some patients have both muscle and skin at the same time.

1, muscle symptoms

Usually the patient feels weak, followed by muscle pain, pain and exercise pain; further, due to decreased muscle strength, various motor dysfunctions and special postures are present, and the symptoms may vary due to the number of muscle lesions, the severity of the disease, and the differences in the location. Generally, there are usually lifting arms. It is difficult to stand after head movement or squatting. The gait is poor. Sometimes, due to the rapid decline of muscle strength, special postures can be presented, such as head sag, shoulders leaning forward, etc. Even turning over, when the pharynx, upper esophageal and ankle muscles are involved, hoarseness and dysphagia may occur; when the diaphragm and intercostal muscles are involved, acute and dyspnea may occur; myocardial involvement may produce heart failure, and the eye muscles may undergo diplopia The diseased muscle texture may be normal or soft, sometimes hard or firm after fibrosis, which may cause joint contracture to affect function. It is also reported that myasthenia gravis syndrome is painless muscle weakness. After exacerbation, the skin above the diseased muscle can be thickened or edematous.

2, skin symptoms

The disease usually emits purple-red spots on the face, especially the upper eyelids, and gradually spreads to the forehead, cheeks, ears, neck and upper chest V-shaped areas, and the scalp and the back of the ear can also be involved. There are obvious dilated dendritic capillaries. Occasionally, there are hair vessels with needle-sized defects at the top of the bend. The edema of the edema is characteristic of the eyelids. The limbs are elbow and especially the metacarpophalangeal joints. There are purple-red papules on the joints of the interphalangeal joints, plaques, which later become atrophy, with telangiectasia, hypopigmentation and overlying small scales, occasionally ulceration, called Gottron sign, also characteristic, visible in the nail folds Capillary dilatation and sputum help to diagnose. In some cases, there may also be a rash on the trunk. It is diffuse or localized with dark red spots or papules. It is located in front of the sternum or between the scapulae or the back and back. It usually has no itching. Pain, abnormal feeling, but a few cases may have itching, the damage is temporary, repeated attacks, and then merge with each other, continue to retreat, there are fine scales, erythema also appears in the oral mucosa.

In chronic cases, there may be multiple keratotic papules, spotted pigmentation, vasodilation, mild skin atrophy and hypopigmentation, called vascular atrophic heterochromic dermatomyositis, occasionally in heterochromatic On the basis of the disease-like rash, the rash is red or even reddish-brown, and the damage is extensive, especially on the head and face. It looks like drunkenness, with more dark brown, gray-colored needles and large pigment spots, and the forest volume is twisted and dendritic. A pile of expanded capillaries, called malignant erythema, often suggest a malignant tumor.

In addition, there may be subcutaneous nodules, calcium deposition discharges the skin to form a leaky tube, and sometimes in atypical cases only purple eye spots appear on the eyelids, one side or both sides or the base of the nose, or diffuse erythema appears in the scalp, Desquamation, hair loss, or urticaria, polymorphous erythema, reticular bluish, Raynaud's phenomenon, etc., some cases are allergic to sunlight.

In addition to the description, pediatric patients are characterized by a history of upper respiratory infections before the onset of symptoms, no Raynaud's phenomenon and scleroderma-like changes, and diffuse or localized calcium deposition in the skin, muscles, and fascia. Common, there are vascular lesions, ulcers and bleeding in the gastrointestinal tract, unlike adults.

In addition, patients may have regular fever, fever may be the initial symptoms of the disease, can also occur during the development of the disease, often irregular low fever, heat in acute cases can be higher, about 40% of cases have fever There may be joint pain, deformity and movement of the elbow, knee and shoulder joints. Most of the fibers secondary to the adjacent muscle lesions are caused by contracture. In some cases, the joint space disappears and the cortical bone is destroyed. 20% have joint lesions, superficial lymph nodes generally have no obvious swelling, a few cervical lymph nodes can be swollen in a cluster; heart involvement cases have cardiac dysfunction, tachycardia or slow, heart enlargement, myocardial damage, atrial fibrillation and heart failure There may also be pleurisy, interstitial pneumonia, about 1/3 of cases of mild to moderate swelling of the liver, moderate tough, digestive tract involving barium meal showing poor esophageal peristalsis, through slow, esophageal dilation, piriform tincture retention, eye Muscle involvement is double vision, the retina sometimes has exudate or hemorrhage, or retinal choroiditis, subarachnoid hemorrhage.

In addition, the disease can overlap with diseases such as SLE and scleroderma.

Dermatomyositis check

There is usually no significant change in blood, sometimes mild anemia and leukocytosis, about one-third of cases have eosinophilia, erythrocyte sedimentation rate increases moderately, serum protein totals do not change or decrease, white globulin ratio decreases, albumin Reduced, alpha 2 and gamma globulin increased.

1. Immunological testing

2, increased creatinine excretion

3. Determination of serum sarcoplasmic enzyme

4, EMG changes: a myogenic atrophy phase, the common is denervated fibrillation, the diseased muscles show denervation, showing irregular and involuntary discharge waveforms, the muscles are not all muscle fibers are also affected, most of them have Normal muscle fibers are scattered, and short-term multi-phase motion units are used when light is applied. When the maximum force is applied, the low-voltage interference phase multi-wave increases.

5. Histological changes

(1) Muscle changes muscles are extensively or partially invaded, muscle fibers are initially swollen, transverse stripes disappear, sarcoplasm is clear, muscle fiber membrane nuclei are increased, muscle fibers are separated, and fractures. In progressive lesions, muscle fibers can be glassy and granular. , vacuole-like degeneration, sometimes even necrosis, or complete disappearance of muscle structure replaced by connective tissue, sometimes with calcium deposition, interstitial inflammatory changes, vasodilation, thickening of the intima, stenosis of the lumen, even embolism, blood vessels There are lymphocytes with the infiltration of plasma cells and histiocytes, which mainly occur in the striated muscle. In some cases, the same lesion can occur in the smooth and myocardium.

(2) Skin changes In the initial stage of edematous erythema, epidermal keratinization, acanthosis atrophy, nail process disappear, basal cell liquefaction degeneration, dermal full-thickness edema, vasodilation, peripheral lymphocyte infiltration, a little between Tissue cells, pigmented incontinence, in progressive lesions, collagen fibers are swollen, homogenized and hardened, thickened blood vessel walls, mucoid degeneration of subcutaneous fat tissue, calcium deposition, further atrophy of the epidermis, and skin atrophy.

6, other

Myoglobin is present in bones and myocardium. There are only a small amount of myoglobin in the blood and urine of the political party. Severe muscle damage can release a large amount of myoglobin. Serum myoglobin measurement can be used as an indicator to measure the degree of disease activity. There are visible hemoglobin-like pigments; when the disease is aggravated, the discharge is increased, and the relief is reduced. It is also reported that the excretion of urinary 3-methylhistidine is a sign of muscle damage, and the disadvantage is that it is non-specific.

Diagnosis and differentiation of dermatomyositis

According to the patient's symmetrical proximal muscle weakness, pain and tenderness, accompanied by characteristic skin lesions such as periorbital-centered purple-red edematous plaque, Gottron's sign and nail-folding, stiff and dilated capillary erythema, generally not diagnosed Difficult, combined with serum sarcoplasmic enzyme and CPK, LDH, AST, ALT and aldolase increased, 24-hour urinary creatine excretion increased, if necessary combined with changes in EMG and biopsy of diseased muscles, can be diagnosed The disease.

Differential diagnosis

1. Systemic lupus erythematosus lesions with buccal edema butterfly erythema, dark erythema of the (toe) nodal surface and edematous purple erythema centered around the nail, finger joint (toe) and palm (?) (toe) joint facial purple erythema and nail folds of the rigid telangiectasia erythema are different; SLE multi-system lesions with the main involvement of the kidney and dermatomyositis mainly with the proximal limb muscle involvement, hoarseness and phagocytosis More common, in addition to the determination of serum sarcoplasmic enzyme and urinary creatine output in patients with dermatomyositis significantly increased, EMG and muscle biopsy can be identified when needed.

2, systemic scleroderma dermatomyositis late lesions such as skin sclerosis, subcutaneous fat tissue calcium deposition, histological also visible connective tissue swelling, sclerosis, skin atrophy, etc., but in the early stage of systemic scleroderma There is Raynaud's phenomenon, swelling of the face and extremities, and atrophy after hardening. The initial lesion of dermatomyositis in muscle lesions is significant, which is a substantial myositis, and in systemic scleroderma, muscle lesions are usually in the late stage. Appear, and for interstitial myositis can be identified.

3, rheumatic polymyalgia (polymyalgia rheumatica), usually occurs in the 40 years of age or older, diffuse pain in the proximal extremity is more than the lower extremities, accompanied by general malaise, patients can not tell the pain from muscles or joints, no muscle weakness, Due to misuse, there may be mild weight loss, normal serum CPK values, normal or mild myopathy changes in myoelectricity.

4, eosinophilic myositis (eosinophilic myositis) characterized by subacute onset myalgia and proximal muscle weakness, serum sarcoplasmic enzyme can be increased, myoelectricity shows changes in myopathy, muscle biopsy shows myositis associated with eosinophilic Sexual infiltration, sometimes focally, is a subtype of the eosinophilia syndrome spectrum.

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