Diagnosis of juvenile dermatomyositis

Non-invasive methods of research

Electrocardiography

The ECG reveals signs of metabolic disturbances in the myocardium, tachycardia. With myocarditis, the conduction delay, extrasystoles, and decreased electrical activity of the myocardium were recorded. Occasionally, ischemic changes in the cardiac muscle are observed-the display of generalized vasculopathy affecting the coronary vessels.

Echocardiography

Echocardiography in myocarditis shows an enlargement of the heart cavities, thickening and / or hyperechogenicity of the walls and / or papillary muscles, a decrease in the contractile and pumping functions of the myocardium, with pericarditis - lamination or thickening of the pericardium.

Ultrasound examination of abdominal organs

According to ultrasound findings nonspecific changes in the liver and spleen: increased vascular pattern and / or echogenicity of the parenchyma.

Spirography

On the spirogram (conducted after 5 years), restrictive changes are noted as a result of a decrease in the strength of respiratory movements.

Radiography of chest organs

On the roentgenogram in most patients, the increase in the vascular pattern is determined, sometimes local, in rare cases - changes in pulmonary interstitium, high diaphragm standing as a result of its paresis. In patients who have not received treatment for a long time, a deformity of the pulmonary pattern is formed.

Electromyography

On the electromyogram (EMG) at normal speed of the nerve impulse, the myogenic character of the changes in the form of a decrease in amplitude and shortening of the duration of action potentials of muscle fibers, spontaneous activity in the form of fibrillation is determined.

Laboratory research

General blood analysis

The general analysis of blood in the acute period of juvenile dermatomyositis, as a rule, is unchanged or there is a moderate increase in ESR (20-30 mm / h), small leukocytosis (10-12 × ^{10 9} / L), normochromic anemia, but often these changes are due to association with infection .

Blood chemistry

Increase in the level of "enzymes of muscle decay" (CK, LDH, ACT, AJIT, aldolase), having diagnostic value. In acute process, progressive lesion of skeletal musculature, the level of CK and LDH exceeds the norm by 10 times or more. The level of CK at the time of primary examination was increased in 2/3 of patients with juvenile dermatomyositis. The LDH level, being a less specific but more sensitive test, is increased in 4/5 patients, but to a lesser extent; on the background of treatment, it lasts longer. The level of ACT exceeds the norm more often and more than ALT. It is advisable to study the level of all 5 enzymes in the blood serum in juvenile dermatomyositis due to the fact that in one patient at a certain time intervals the level of only one of them can be increased.

Immunological examination

In the active period of the disease, some immunological changes are revealed. The determination of myositis-specific antibodies in practice is not used due to the low frequency of their detection in the juvenile form of the disease. Only with interstitial pulmonary syndrome, the definition of anti-jo-1 antibodies is of practical value.

Currently, positive ANF in the active phase of the disease is detected in 50-86% depending on the sensitivity of the technique (usually not in such a high titer as in systemic lupus erythematosus), usually reaching 1: 40-1: 80. Approximately 1/4 of patients in the active period can be detected an increase in the level of IgG, in every tenth patient - a positive rheumatoid factor. With a pronounced vasculitis syndrome, antibodies to cardiolipins (ACL) are positive.

Invasive methods of research

In biopsies of muscles, there are changes in inflammatory and degenerative nature: cellular infiltration between muscle fibers and around small vessels with a predominance of lymphocytes, the involvement of histiocytes and plasma cells; necrosis of muscle fibers with loss of transverse striation, elements of regeneration. In the chronic process, atrophy of muscle fibers predominates, signs of interstitial fibrosis.

In our opinion, in typical cases, the diagnosis is established based on the clinical picture and laboratory data. EMG data and muscle biopsies do not always match the established criteria due to artifacts and sclerotic changes that distort the results, and therefore it is necessary to resort to these diagnostic methods in disputable, unclear cases.

Differential diagnostics

Differential diagnosis of juvenile dermatomyositis is carried out with a large number of diseases.

Juvenile polymyositis very rarely develops in childhood. It is characterized by weakness of the proximal and distal parts of the limbs, hypotension, dysphagia. The disease is more often with a chronic course, it is difficult to treat glucocorticosteroids. To confirm the diagnosis, a muscle biopsy is necessary. Poliomyositis in the first year of life can be a manifestation of intrauterine infection.

Infectious myositis is caused by viruses, protozoa and bacteria. Viral myositis causes influenza A and B viruses, coxsack B, the disease lasts 3-5 days, accompanied by severe myalgia, fever, catarrhal and general symptoms.

The clinical picture of toxoplasmosis resembles dermatomyositis.

Trichinosis is accompanied by fever, diarrhea, abdominal pain, eosinophilia, edema of paraorbital space and muscles, more often face, neck and chest.

Neuromuscular diseases and myopathies (Duchenne's myodystrophy, Myasthenia gravis, myotonia, etc.) are distinguished by the absence of typical skin manifestations.

Duchenne's myodystrophy differs slowly progressive muscular weakness (predominantly proximal) in the absence of muscle tightening, a hereditary character.

For Myasthenia gravis is characterized by the involvement of the eye and distal muscles of the limbs, reducing the feeling of weakness after the appointment of cholinergic drugs.

Myositis in other systemic diseases of connective tissue, in particular in systemic lupus erythematosus, cross syndromes, systemic scleroderma, is quite pronounced, accompanied by myalgia, distinct muscle weakness and an increase in the level of "enzymes of muscle decay". In such cases, the severity of other clinical symptoms, the presence of immunological markers of other systemic connective tissue diseases, are important in diagnosis.

Ossifying progressive myositis (Munichmayer disease) is a rare hereditary autosomal dominant disease manifested by fibrosis and calcification of large axial muscles, leading to stiffness and severe disability. The process begins with the muscles of the neck and back, extending to the limbs.

It should be remembered that muscle weakness can be a manifestation of certain endocrinopathies (hypo- and hyperthyroidism, hypo- and hyperparathyroidism, diabetes mellitus, steroid myopathy, Addison's disease, acromegaly), metabolic disorders (glycogen accumulation diseases, mitochondrial myopathies), toxic and drug myopathy D-penicillamine, colchicine, etc.)

[1], [2], [3], [4], [5]