POLYMYOSITIS AND DERMATOMYOSITIS

Polymyositis and dermatomyositisis a chronic rheumatic disease involving striated and in rare cases smooth muscles and skin. If the skin is not damaged, the disease is called polymyositis. It may occur at any age, mainly in women.

Pathogenesis. The basic cause of polymyositis is unknown. Lymphocyte-mediated muscle cell damage is thought to be the underlying mechanism. Also, autoantibodies to extractable nuclear antigens PM_X and JO-1 are said to be most specific for this disease.

Pathology. Clinically symmetrical, proximal, upper and lower extremity muscle weakness is characteristic.

Striated muscles, the muscles of the pharynx, larynx, diaphragm, ocular muscles are involved. Degeneration, calcinosis, necrosis, edema, cellular reactions are observed. Microscopically, edema and a scant mononuclear infiltrate appear early in the disease. Later, a prominent mononuclear infiltrate occurs in conjunction with interstitial fibrosis and myofiber degeneration.

Skin. An erythematous, sometimes scaling rash occurs in the malar region and is similar to that seen in lupus. However, it also is found on the upper chest, neck, forehead, and shoulders. Heliotrope rash, a lilac discoloration on the upper eyelids, is said to be pathognomonic. Microscopically, edema, a perivas-

cular infiltrate, and liquefactive degeneration of the dermoepidermal junction are similar to those seen in lupus.

Combination of degenerative, inflammatory and sclerotic changes is observed in the heart, lungs, alimentary tract. Hyperplasia against the background of plasmatization is observed in the immune organs.

A variety of disease subsets are described. These include:

• adult polymyositis;

• adult dermatomyositis;

• polymyositis or dermatomyositis associated with malignancy;

• childhood dermatomyositis (associated with immune complex deposition and vasculitis);

• polymyositis or dermatomyositis associated with other autoimmune disease.

Clinico-morphological forms:

1) primary (idiopathic),

2) secondary (tumor).

Each form may be acute, subacute, constantly relapsing and chronic. Primary form in children is caused by genetic factor. Secondary form is frequently observed in cancer of ovaries, stomach, lungs, breast.

Stages of individual work in class Study and describe macrospecimens

Acute verrucous endocarditis. Describe the cusps of the mitral valve; the appearance, size of the plaques on the surface of the valve, their colour; characterize the condition of the myocardium, the outcome of these plaques on the cusps of the valve.

Recurrent verrucous endocarditis. The appearance of thickened cusps of the valve (pay attention to the short and thickened tendinous strings). Describe the appearance of the thrombotic masses, the condition of the myocardium.

Fibroplastic endocarditis. Characterize the cusps of the aortic valve and the mitral valve cusps, their colour, transparency, thickness, condition of the cavity of the left ventricle.

Stenosis of the ostium of the mitral orifice. Describe the cusps of the mitral valve, their thickness, colour; the appearance and width of the opening. Due to what process did stenosis develop in the valve? Describe the condition of the myocardium of the left ventricle, its colour. The size, type of hypertrophy.

Fibrinous pericardium (Cor villosum). The appearance of the heart, changes of the pericardium. What does the heart look like? Name the types of pericarditis in rheumatic disease and their outcome.

Glomerulonephritis in lupus erythematosus. Describe the appearance of the kidney, condition of the incision.