Polymyositis

Swelling of many muscles is called as polymyositis. Various genetic and environmental causes are postulated for occurrence of this rare disease. Myositis can be associated with various inflammatory connective tissue diseases such as systemic lupus erythematosus and Sjogren's syndrome. It can occur at any age (average 50-60 years) and is more common in females. Children can also be affected. Polymyositis associated with skin lesions is known as dermatomyositis.

Features
Diminished muscle endurance, symmetric muscular weakness and fatigue develop insidiously over 3-6 months. There is no pain in muscles. Low grade fever and weight loss may accompany. Muscle weakness usually starts in shoulder and pelvic girdle muscles and spreads to thighs and upper arms. Patients are unable to get up, climb stairs or reach overhead objects. Extensive muscle involvement ultimately makes the patient wheel-chair bound. Involvement of throat muscles can cause difficulty in swallowing whereas those of diaphragm leads to breathing difficulties. Skin involvement in dermatomyositis may precede muscle weakness and may present without muscle problems. There are many peculiar skin rashes occurring on face, hands, neck, shoulder and front of chest wall.

Other Features

  1. Joint pains, arthritis
  2. Cough and breathlessness due to involvement of lungs and muscles of breathing
  3. Difficulty in swallowing, abdominal pain, unsatisfactory bowel, diarrhea and bleeding due involvement of gastrointestinal tract
  4. Irregular pulse due to heart involvement
  5. Osteoporosis due to immobilization, glucocorticoids and other factors


Investigations
A good clinical examination from a rheumatologist or neurologist is desirable. Blood examination for muscle enzymes (creatinine kinase), myoglobin and autoantibodies gives valuable clues to diagnosis. Intramuscular injection should be avoided before blood tests as it can increase muscle enzyme levels. Electromyography (EMG) is a nonspecific diagnostic tool that must be performed after blood examination. Magnetic Resonance Imaging (MRI) shows swelling of muscle in active myositis. Biopsy of symptomatic muscle is essential for diagnosis. Interpretation of biopsy sample needs a pathologist with special expertise in this field. 10% cases of dermatomyositis are associated with cancer. All cases must, therefore, be investigated for occult cancer.

Therapy
Early diagnosis and treatment is essential for good therapeutic outcome. High dose glucocorticoids alongwith methotrexate is mainstay of therapy at present. The dose of glucocorticoids is tapered later on. Azathioprine can be used alone or in combination with methotrexate. Cyclophosphamide is used in associated lung disease. A few case reports indicate use of tacrolimus, mycophenolate and rituximab in resistant cases.Therapy: Early diagnosis and treatment is essential for good therapeutic outcome. High dose glucocorticoids alongwith methotrexate is mainstay of therapy at present. The dose of glucocorticoids is tapered later on. Azathioprine can be used alone or in combination with methotrexate. Cyclophosphamide is used in associated lung disease. A few case reports indicate use of tacrolimus, mycophenolate and rituximab in resistant cases.

Exercise
Exercise is an essential part of therapy. Passive exercises must be commenced at an early active stage under supervision of an expert physiotherapist. Passive exercises are safe and beneficial but overuse of muscles must be avoided in this phase. Strengthening exercises should be started at a later stage after control of disease activity. Exercise: Exercise is an essential part of therapy. Passive exercises must be commenced at an early active stage under supervision of an expert physiotherapist. Passive exercises are safe and beneficial but overuse of muscles must be avoided in this phase. Strengthening exercises should be started at a later stage after control of disease activity.

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