Juvenile dermatomyositis

Introduction to juvenile dermatomyositis Juvenile dermatomyositis (JDM) is an immune-mediated multisystem disease characterized by acute or chronic non-suppurative inflammation of the striated muscle and skin. Early stages of occlusive vascular disease with varying degrees of calcification About 10% combined with other connective tissue diseases, such as JRA, SLE, scleroderma, etc., a small number of malignant tumors. The main cause of death is respiratory failure and gastrointestinal ulcers, bleeding. basic knowledge The proportion of illness: 0.001% Susceptible people: children Mode of infection: non-infectious Complications: dysphagia, paralytic ileus, jaundice, liver enlargement

Causes of juvenile dermatomyositis

Virus infection (45%):

The etiology and pathogenesis of this disease are unknown, and its pathogenesis is related to infection and immune dysfunction. A variety of infections, especially viral infections, especially Coxsackie virus and dermatomyositis are involved, and infection causes lymphocyte release of cytokines and other mechanisms. Muscle fiber.

Body factor (55%):

At the same time, muscle protein is denatured and antigenic, and the autoantigen antibody reaction may also play a role. It is generally considered that the disease is a skeletal muscle disease caused by cell-mediated immune disorders, and children with dermatomyositis HLA-B8 and DR3 Significant increase, but the relationship with family inheritance has not been determined.

Pathogenesis

Extensive vasculitis is the main pathological change of dermatomyositis in children. Small arteries, venules and capillaries can be seen with vascular degeneration, embolism, multiple infarction. Under electron microscope, vascular degeneration is mainly caused by endothelial cell changes, endothelial cell swelling, degeneration and necrosis. Causes platelet accumulation, thrombosis and stenosis and obstruction. This vascular change can be seen in the skin, muscle, subcutaneous tissue, gastrointestinal tract, central nervous system and visceral capsule. Skin changes manifest as epidermal atrophy, basal cells Liquefaction and degeneration, dermal edema, chronic inflammatory cell infiltration, collagen fiber breakage and fragmentation, and the underlying epithelial capillaries can be seen to expand, increase, decrease in number and become distorted due to endothelial swelling. In severe cases, use the naked eye. It can be seen that muscle tissue due to small muscle vascular lesions around the muscle bundle, the muscle fibers vary in thickness, degeneration, necrosis, longer course, muscle fiber atrophy or fibrous connective tissue replacement, calcareous, gastrointestinal vascular damage can be Form ulcers, bleeding and perforation.

Juvenile dermatomyositis prevention

1. The disease is related to infection and immune dysfunction. Therefore, active prevention and treatment of infections, especially viral infections, especially Coxsackie virus infection, should reduce the incidence of this disease;

2. The disease can be related to the environment, and is closely related to the season and geographical location. Therefore, pay more attention to the environment in which you live.

3. Vaccines, drugs and bone marrow transplants can also induce JDM, which requires us to be alert to the use and injection of drugs.

Juvenile dermatomyositis complications Complications, difficulty swallowing, paralytic ileus, jaundice, liver enlargement

Involvement of the throat muscle can cause difficulty in swallowing, diffuse hemorrhagic inflammation of the digestive tract mucosa or acute mesenteric artery embolization, gastrointestinal perforation, paralytic ileus, jaundice, hepatomegaly, lymphadenopathy, Raynaud's phenomenon, splenomegaly Major, advanced muscle atrophy and joint contracture.

Juvenile dermabrasion symptoms Common symptoms Lymph node enlargement Abdominal distension Abdominal pain Splenomegaly palsy intestinal obstruction

Generally occult onset, 1/3 acute onset, irregular fever, 38 ~ 40 ° C, often complained of fatigue, discomfort, joint pain, anorexia and weight loss, irritability, reduced activity.

Muscle symptoms

The child complained of mild myalgia or muscle stiffness, muscle weakness, more common in the lower extremity limb muscles when the onset, resulting in the inability to walk, can not go up the stairs, the cervical flexor and back muscles can not lift and maintain the sitting position, the diseased muscles Symmetrical distribution, obvious proximal muscles, such as hip, shoulder, cervical flexor and abdominal muscles; affected muscles are edematous, slightly hard, tender tenderness; muscle weakness, children can not sit up from the supine position, can not stand from the seat From the beginning, you can't squat or squat, you can't stand up, it's difficult to get up and down the stairs; the severe involvement of the distal muscles of the limbs, the children can not move at all, 10% of the children's throat muscles are involved, leading to difficulty swallowing; 5% of children's facial muscles and eyes External muscle involvement leads to less facial expression, valgus valgus, deep sacral reflexes, and muscle atrophy and joint contracture in the advanced stage.

2. Skin symptoms

3/4 children have typical skin changes, which can be the first symptom, or a few weeks after the muscle symptoms appear:

(1) rash: the upper eyelid skin becomes purple-red with edema, the face is diffused purple or purple, the neck and upper chest "V" area, the trunk and the extremities can be diffuse or limited. Dark red spots, the degree of rash and duration of rash, pigmentation can be left after the rash subsides.

(2) Gottron plaque: the symmetry change of the joint extension side, which is a lustrous erythema-like atrophic scaly plaque. The skin atrophy area is pale pink, and the early skin thickening is white, so it is also called fire cotton plaque, Gottron plaque. Common in the proximal interphalangeal joint, second metacarpophalangeal joint, distal interphalangeal joint; toe is rare; elbow, knee, ankle joint extension can also be involved.

(3) nail wrinkles: the skin is obviously red, the wrinkles of the capillaries are dilated, the capillaries are thickened, bent and interrupted.

(4) Late stage: It can produce subcutaneous calcification and skin ulcers, and discharge white calcium salt from the rupture.

3. Gastrointestinal symptoms

Oropharyngeal ulcer, total abdominal pain, black feces, occasional hematemesis, diffuse hemorrhagic inflammation of the digestive tract mucosa or acute mesenteric artery embolization; free gas under the armpit when the gastrointestinal tract is perforated; suspected and paralyzed intestine during abdominal distension obstruction.

4. Other

May have jaundice, liver and liver dysfunction, lymphadenopathy, Raynaud's phenomenon, splenomegaly, often involving the heart, lungs, genitourinary system and central nervous system.

Examination of juvenile dermatomyositis

Laboratory inspection

1. Blood: leukocytosis in the acute phase and anemia in the late stage.

2. Acute phase reactants : ESR increased, 2 and gamma globulin increased, CRP was positive, but the change was mild.

3. Serum enzymology examination : creatine kinase (CK), lactate dehydrogenase (LDH), aspartate aminotransferase (AST) and so on, CK isoenzyme CK-MM increased.

4. Antinuclear antibody : ANA 50% positive, but no dsDNA and anti-Sm antibody positive, can have specific anti-Jo-1 antibody.

Film degree exam

1. X-ray examination : calcification around the bone joint, or diffuse soft tissue and skin calcification.

2. Electromyography : Myogenic changes, manifested as: spontaneous fibrillation potential at rest, positive sharp wave, insertion irritability, short time limit during contraction, low amplitude, multiphase potential, repeated high during stimulation Frequency discharge.

3. MRI : It can show the location and extent of muscle abnormalities, which is helpful for monitoring the condition and guiding the muscle biopsy site.

4. Muscle biopsy : generally deltoid or quadriceps, lesions confirmed by electromyography or MRI, no muscle atrophy, specimens should be larger (2 ~ 3cm); inappropriate parts and inappropriate Specimen size can make the muscle biopsy results negative, and the disease should not be done in the late stage of the disease. Therefore, the lesions are no longer specific. The biopsy specimens can be seen: perivascular inflammatory cell infiltration, muscle fiber atrophy and necrosis around the muscle bundle , muscle fiber regeneration phenomenon.

Diagnosis and diagnosis of juvenile dermatomyositis

diagnosis

Typical dermatomyositis diagnosis is not difficult, with a typical rash, symmetric proximal muscle weakness, combined with serum muscle enzymes, EMG and muscle biopsy changes, you can make a diagnosis, currently applying Bohan's criteria in 1975:

1. Symmetrical proximal muscle weakness: may be associated with difficulty swallowing and respiratory muscle weakness.

2. Typical skin changes: including upper eyelids with purplish red and edema around the eyelids; and red scaly rash on the dorsal side of the metacarpophalangeal and proximal interphalangeal joints (Gottron's sign).

3. Laboratory tests: Increased serum skeletal muscle enzyme activity, especially creatine kinase, aspartate aminotransferase and aldolase.

4. EMG abnormalities:

1 low potential, short time-limited multiphase wave;

2 fibrillation potential, positive spikes, insertion potential extension;

3 When the time is quiet, the high amplitude is abnormally discharged.

5. Muscle biopsy: typical myogenic damage.

Differential diagnosis

1. Myositis after infection: Some viral infections, especially influenza A, B and Coxsackie B, may cause acute transient myositis, which may increase transient serum muscle enzymes and recover completely after 3 to 5 days. In addition, trichinosis, toxoplasmosis and staphylococcal infection can cause similar symptoms to dermatomyositis and should be identified.

2. Myasthenia gravis: It should be differentiated from polymyositis without rash. The disease is characterized by generalized muscle weakness. The muscles of the affected muscles are aggravated after prolonged or repeated activities, often accompanied by drooping eyelids, often in the morning and evening. Heavy, serum muscle enzyme and muscle biopsy are normal, anti-acetylcholine receptor (AchR) antibody positive, neostigmine test can be identified.

3. Progressive muscular dystrophy: The disease is male, with typical duck gait and gastrocnemius pseudohypertrophy, with a clear family history.

In addition, it should be differentiated from systemic lupus erythematosus and mixed connective tissue disease in rheumatic diseases. Others should be differentiated from diseases characterized by muscle weakness and paralysis, such as multiple radiculitis, polio and myelitis. .

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