Polymyositis and Dermatomyositis

  Prepared by Dr Sawsan Abdullah Al Abdulhai  Consultant in Internal Medicine and Rheumatology     Polymyositis and Immune-Mediated Dermatomyositis Polymyositis and dermatomyositis                              Definition: Polymyositis is an uncommon disease that causes muscle weakness. People of all ages can develop it, but it most often affects adults from their late forties to early sixties. In children, it generally appears between the ages of 5 and 15. The disease is 2.5 times more common in women than in men, while its prevalence is equal among boys and girls. When myositis is accompanied by skin inflammation, the condition is called dermatomyositis. It can affect the skin in several ways, most commonly around the small joints of the hands, where Gottron's papules appear, and around the eyes and cheeks, where it is known as a heliotrope rash. Symptoms Symmetrical weakness of the proximal muscles, including the thigh and upper-arm muscles. This causes difficulty climbing stairs, rising from a seated position, lifting objects overhead, or even raising the hands to comb one's hair. Muscle strength declines gradually over a period of weeks or months. You should see a physician if you experience unexplained muscle weakness—that is, weakness not caused by unusual muscular exertion, such as strenuous exercise. Causes Unfortunately, the exact cause of myositis is unknown. It is believed, however, to result from autoimmune disorders in which the immune system mistakenly attacks the body's own tissues.  Complications of Dermatomyositis A small number of patients may experience complications, such as difficulty breathing if the chest muscles are affected, or difficulty swallowing if the esophageal muscles are affected. In other cases, inflammation of the heart muscle may cause an irregular heartbeat and, rarely, congestive heart failure. Interstitial lung disease may also occur, resulting in scarring of lung tissue; with dermatomyositis, the patient may develop a cough and shortness of breath. Both conditions are associated with malignancies in a small number of cases, particularly cancers of the cervix, pancreas, ovaries, breasts, gastrointestinal tract, and urinary bladder. This association is relatively more common among patients with dermatomyositis than among those with polymyositis alone. The treating physician must therefore conduct appropriate tests, including clinical examinations and imaging, to rule out any of these diseases. Diagnosis of dermatomyositis If myositis is suspected, some of the following tests may be required:

• Certain blood tests:

A blood test can detect elevated levels of muscle enzymes, which indicate muscle damage, and may also identify specific autoantibodies associated with the different symptoms of myositis.

• Electromyography (EMG):

The procedure involves inserting thin needles through the skin into the muscle. Changes in the pattern of electrical activity may confirm the diagnosis.

• Muscle biopsy:

Surgical removal of a small sample of muscle tissue - with the physician selecting the muscle, usually a thigh muscle - for laboratory analysis to identify the type of inflammation and the extent of muscle damage.

• Skin biopsy:

The physician may take a small skin sample to identify the type of inflammation.

• Magnetic resonance imaging (MRI):

The treating physician may sometimes request magnetic resonance imaging to assess inflammation in the muscles. Treatment The treating physician generally develops a treatment plan based on your symptoms. Following the treatment can improve muscle strength and function and clear the skin rash. The earlier treatment for immune-mediated myositis begins, the better the outcomes and the lower the likelihood of complications. Medicines Treatment includes several medications. The physician selects the treatment most appropriate for each patient's condition based on the symptoms and response to treatment. More than one medication is usually used at the same time, and the physician may need to replace a medication if the disease does not respond to it. These medications include, but are not limited to, corticosteroids, which are highly effective in controlling the symptoms of myositis. Cortisone treatment begins at a high dose, which the physician then gradually reduces to lessen the likelihood of side effects. It is therefore essential to follow the physician's instructions precisely. The two medications most commonly used to treat polymyositis are methotrexate and azathioprine. Other medications prescribed for myositis include mycophenolate mofetil, cyclosporine, tacrolimus, and rituximab (Rituximab). Immunoglobulin therapy is one treatment option. When monitoring a patient's condition, the physician primarily assesses improvement in muscle strength while tracking muscle enzyme levels in blood tests. Physical Therapy The patient may need exercises to maintain strength and activity, and a physiotherapist will provide instruction on them. Adapting to the disease and family support Patients should keep their physicians informed of any new signs or symptoms they experience. The body generally recovers and muscles gradually regain their strength. Patients should continue their daily activities as much as possible, as this helps restore their energy, while resting whenever they feel tired rather than waiting until they are exhausted. They should also avoid isolation and remain close to family and friends to maintain a stable emotional state that supports further recovery, God willing.