Dermatomyositis definition

Dermatomyositis is a diffuse inflammatory pathology of connective tissue with a progressive course, characterized by the defeat of smooth and striated muscle fibers with impaired motor functions, skin involvement, small vessels and internal organs. In the absence of skin syndrome, the presence of polymyositis is indicated. Clinic of dermatomyositis is characterized by polyarthralgia, expressed by muscle weakness, fever, erythematous-spotted rash, skin calcifications, visceral symptoms. Diagnostic criteria for dermatomyositis are clinical, biochemical, electromyographic indicators. The main therapy is hormonal, the course of the dermatomyositis is undulating.

The etiological relationship of dermatomyositis with a viral infection (picornaviruses, Coxsackie viruses) and genetic conditioning is assumed. Chronic persistence of viruses in the muscles and antigenic similarity between viral and muscle structures causes an immune response with the formation of autoantibodies to muscle tissue. Starting points to the development of dermatomyositis can serve as hypothermia, infectious exacerbation, stress, hyperthermia, hyperinsolation, drug provocation (vaccination, allergy).

Classification of dermatomyositis

Dermatomyositis and polymyositis belong to the group of idiopathic inflammatory myopathies. Secondary paraneoplastic (tumor) dermatomyositis occurs in 20-30% of cases. The course of dermatomyositis can be acute, subacute or chronic.

In the development of pathology, the period of nonspecific precursors (prodromal), clinical manifestations (manifest) and the stage of complications (terminal, dystrophic, cachectic) are distinguished. Dermatomyositis can occur with varying degrees of activity of inflammation (from I to III).

Symptoms of dermatomyositis

The clinic of dermatomyositis develops gradually. At the beginning of the disease there is a progressive weakness in the muscles of the limbs, which can grow for years. Acute onset is less common for dermatomyositis. The main clinical manifestations may be preceded by the appearance of skin rashes, polyarthralgia, Raynaud's syndrome. The defining symptom in the clinic of dermatomyositis is the defeat of the striated muscle. There is a weakness in the muscles of the neck, the proximal parts of the lower and upper extremities, which leads to difficulties in performing daily activities. In severe lesions, patients hardly lift themselves up in bed, can not hold their heads, move independently and hold objects in their hands.

The involvement of the pharynx musculature and the upper digestive tract is manifested by speech disorders, swallowing disorders, and suppuration; The defeat of the diaphragm and intercostal muscles is accompanied by a violation of the ventilation of the lungs, the development of congestive pneumonia. A characteristic sign of dermatomyositis is the defeat of the skin with various manifestations. There is a development of periorbital edema, erythematous-spotted rash over upper eyelids, in the region of cheekbones, nasolabial folds, nose wings, upper back, sternum, joints (knee, elbow, metacarpophalangeal, interphalangeal).

Typically, the presence of Gotthron's symptom - flaky erythematous spots on the skin of the fingers, flaking and redness of the palms, brittleness and streakiness of the nails, okolonogevoy erythema. A classic feature of dermatomyositis is the alternation of foci of depigmentation and pigmentation in combination with telangiectasias, dryness, hyperkeratosis and atrophy of skin areas (poikilodermatomyositis) on the skin. From the side of the mucous membranes with dermatomyositis, there are phenomena of conjunctivitis, stomatitis, edema and hyperemia of the palate and posterior pharyngeal wall. Sometimes there is an articular syndrome with knee, ankle, shoulder, elbow, wrist joints, small joints of the hands. With juvenile dermatomyositis, intradermal, intrafacial and intramuscular calcifications may appear in the projection of the pelvic, upper arm, buttocks, and joints. Subcutaneous calcifications can lead to ulceration of the skin and the release of calcium deposits outwards in the form of a crumbly mass.

Among the systemic manifestations of dermatomyositis, there are cardiac lesions (myocardiofibrosis, myocarditis, pericarditis); Lungs (interstitial pneumonia, fibrosing alveolitis, pneumosclerosis); Gastrointestinal tract (dysphagia, hepatomegaly); Kidneys (glomerulonephritis), the nervous system (polyneuritis), endocrine glands (hypofunction of the adrenal glands and gonads).

Diagnosis of dermatomyositis

The main diagnostic markers of dermatomyositis are the characteristic clinical manifestations of skin and muscular damage; Pathomorphological transformation of muscle fibers; Increased serum enzyme levels; Typical electromyographic changes. Additional (auxiliary) criteria for diagnosis of dermatomyositis include dysphagia and calcification.

The reliability of the diagnosis of dermatomyositis is not in doubt with the presence of 3 basic diagnostic criteria and skin rash or 2 basic, 2 auxiliary criteria and skin manifestations. The probability of dermatomyositis can not be ruled out when skin lesions are detected; With a combination of any 2 other main manifestations, as well as the combination of any basic and 2 auxiliary criteria. To establish the fact of polymyositis, it is necessary to have 4 diagnostic criteria.

The picture on the part of the blood is characterized by moderate degree of anemia, leukocytosis, neutrophil shift of the leukocyte formula to the left, the increase in ESR in accordance with the activity of the process. Biochemical markers of dermatomyositis are an increase in the levels of α2- and γ-globulins, fibrinogen, myoglobin, sialic acids, haptoglobin, seromucoid, transaminases, aldolase, reflecting the severity of muscle tissue damage. Immunological examination of blood in dermatomyositis reveals a reduced complement fissure, a decrease in the number of T-lymphocytes, an increase in the level of immunoglobulins IgG and IgM with decreasing IgA, a small amount of LE cells and antibodies to DNA, a high content of myositis-specific antibodies, the presence of nonspecific antibodies to thyroglobulin, myosin, endothelium etc.

In the study of musculoskeletal biopsies, a picture of severe myositis, fibrosis, degeneration, inflammatory infiltration of muscle fibers, loss of transverse striation is determined. Electromyogram with dermatomyositis fixes increased muscular excitability, short-wave polyphase changes, fibrillar oscillations at rest. On radiographs of soft tissues are visible areas of calcification; When lung radiography is determined by an increase in the size of the heart, calcification of the pleura, interstitial fibrosis of the lung tissue. In the bones, moderate osteoporosis is revealed.

Treatment of dermatomyositis

When the respiratory muscles and palatine muscles are affected, it is necessary to ensure the functions of adequate breathing and swallowing. To suppress inflammatory phenomena with dermatomyositis, corticosteroids (prednisolone) are administered under the control of blood serum enzymes and the clinical state of the patient. In the course of treatment, the optimal dosage of corticosteroids is selected, the drugs are taken for a long time (1-2 years). It is possible to carry out steroid pulse therapy. The anti-inflammatory scheme with dermatomyositis can be supplemented by the appointment of salicylates.

In case of ineffectiveness of corticosteroid therapy of dermatomyositis, immunostimulators of cytostatic action (methotrexate, cyclosporine, azathioprine) are prescribed. To control skin manifestations of dermatomyositis, 4-aminoquinoline derivatives (hydroxychloroquine) are used; For normalization of muscular functions - injections of neostigmine, ATP, cocarboxylase, B vitamins. In therapy of dermatomyositis, intravenous immunoglobulin, lymphocytapheresis and plasmapheresis sessions are used. In order to prevent muscle contractures, a complex of exercise therapy is prescribed.

Prognosis and prevention of dermatomyositis

With the running course of dermatomyositis, the lethality in the first 2 years of the disease reaches 40%, mainly due to the defeat of respiratory muscles and gastrointestinal bleeding. With a severe prolonged nature of dermatomyositis, contractures and deformities of the limbs develop, leading to disability. Timely intensive corticosteroid therapy suppresses the activity of the disease and significantly improves the long-term prognosis. Activities that prevent the development of dermatomyositis have not been developed. Among the measures of secondary prevention of dermatomyositis include clinical examination of a rheumatologist, maintenance therapy with corticosteroids, reduction of reactive hypersensitivity of the organism, sanitation of focal infection.