Difficulty climbing stairs

Introduction Patients with polymyositis feel difficult when they step up and stand up from their seat. Polymyositis is a systemic connective tissue disease characterized by inflammation, degeneration, and other changes in the muscle tissue (the skin is also often affected, ie, dermatomyositis), resulting in symmetrical muscle weakness and a certain degree of muscle atrophy, mainly in the limbs. muscle.

Cause

The cause is unknown, may be caused by autoimmune reaction, and it has been found that there is a deposition rate of IgM, IgG, C3 in skeletal muscle, especially in children with dermatomyositis. Cell-mediated immune responses play an important role in muscle, and viruses may also be involved in disease: microRNA-like structures have been found in muscle cells, and electron microscopy is also present in myocytes and endothelial cells in the skin and muscle wall. A tubular inclusion body resembling a paramyxovirus nucleocapsid was found. A related phenomenon of malignant tumors and dermatomyositis (much more polymyositis) suggests that tumors can cause myositis, which is the result of an immune response against a common antigen of muscles and tumors.

The disease is not uncommon, the incidence is lower than systemic lupus erythematosus and progressive systemic sclerosis, but higher than nodular polyarteritis. The ratio of men to women is 1:2. People of any age group can develop the disease, but the highest incidence rate is 40 to 60 years old, or 5 to 15 years old children.

an examination

Related inspection

Static bone imaging bone and joint MRI examination bone palpation

Laboratory inspection

Laboratory tests are helpful for the clinic. However, lack of specificity, erythrocyte sedimentation rate often increases. A small number of patients have antinuclear antibodies or lupus cells, especially those with other connective tissue diseases, and the positive rate is higher in about 60% of patients with anti-thymocyte antigen (RM-1) antibody positive or anti-thymocyte extract (Jo -1) ) antibody positive. The relationship between these antibodies and the pathogenesis of the disease is unclear, although the Jo-1 antibody is an important marker associated with fibrotic alveolitis and pulmonary fibrosis. Elevated serum muscle enzymes, especially transaminase, creatine kinase (CR) and aldolase. Regular examination of CK levels can help guide treatment, and effective treatment can reduce elevated enzymes. However, in patients with chronic myositis and extensive muscle wasting, the level of muscle enzymes is normal even during active periods.

diagnosis

There are five main diagnostic criteria:

(1) The proximal muscle is weak.

(2) Characteristic rash.

(3) The serum muscle enzyme content is increased.

(4) Muscle biopsy changes (often decisive).

(5) Special electromyography triad: spontaneous fibrillation potential and positive sharp wave and insertion irritability increased; active contraction showed multi-phase short-term potential; repeated high-frequency discharge caused by mechanical stimulation. Electromyography is generally single-measurement, so muscles with abnormal EMG should be selected for biopsy.

Differential diagnosis

Differential diagnosis of difficult steps:

1, the 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 are Raynaud's phenomenon, swelling of the face and extremities, and atrophy after hardening. The initial lesion of dermatomyositis is already significant, which is a substantial myositis. In systemic scleroderma, muscle lesions are usually in the late stage. Appear, and for interstitial myositis can be identified.

2, 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 systemic fatigue, 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.

3, 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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