Definition

Polymyositis is a chronic autoimmune and inflammatory disease characterized by muscle weakness, particularly in muscles close to the center of the body. As the disease progresses, other muscles throughout the body can also weaken.

Autoimmune diseases occur when the immune system mistakenly attacks healthy cells in the body. Polymyositis is part of a group of muscle disorders known as inflammatory myopathies. In polymyositis, muscle weakness is symmetrical, affecting both sides of the body. The muscles most commonly affected include those in the upper arms, thighs, shoulders, pelvis, and torso.

When muscles become irritated and inflamed, the muscle tissue gradually breaks down, leading to weakness. This can make it difficult for patients to perform simple movements, such as climbing stairs, standing up from a sitting position, lifting objects, or reaching overhead.

Causes

The exact cause of polymyositis is unknown, but it is believed to involve an autoimmune reaction. Immune cells that normally fight off foreign invaders in the body mistakenly attack healthy muscle tissue. This damages a layer of muscle tissue over time, leading to muscle weakness. This complex autoimmune process can affect not only skeletal muscles but also other muscles in the body as the disease progresses.

Additionally, viral infections such as HIV, hepatitis C, or coxsackievirus are suspected to be associated with the muscle inflammation seen in this disease.

Risk Factor

Several factors can increase the risk of developing polymyositis, including:

• This disease typically affects people over 20, most commonly between the ages of 31 and 60.
• Women are twice as likely to develop polymyositis as men.
• Polymyositis is more common in Black individuals than in White individuals.
• Other autoimmune diseases, such as celiac disease in the gastrointestinal tract or rheumatoid arthritis.
• Medications, such as the blood pressure-lowering hydralazine, ACE inhibitors, the anti-arrhythmic drug procainamide, and certain anti-epileptic drugs.

Polymyositis may also be associated with other diseases, including breast cancer, lung cancer, or colon cancer. This is because having polymyositis can increase a patient's risk of developing cancer within 2-5 years after diagnosis.

Symptoms

Muscle weakness is the most common symptom reported by patients. Polymyositis initially affects muscles near the center of the body, such as the neck, shoulders, upper arms, thighs, or pelvis. The muscle weakness is symmetrical, affecting both the left and right sides of the body, and progresses over time. Weakness can develop over a period of 3-6 months and gradually worsen. Other muscles, such as those in the forearms, wrists, hands, feet, as well as the respiratory and digestive muscles, can also be affected as the disease progresses.

Other symptoms and signs that may appear with polymyositis include:

1. Difficulty standing up from a sitting position, getting out of bed, climbing stairs, or lifting objects.
2. Muscle pain and stiffness; in some cases, muscles may become tender to the touch.
3. General body weakness.
4. Fever.
5. Difficulty swallowing if the muscles involved in digestion are affected.
6. Shortness of breath, especially if the heart and lung muscles are involved.
7. Irregular heartbeat.
8. Swallowing difficulties can lead to weight loss and nutritional problems.
9. If polymyositis is accompanied by skin abnormalities (dermatomyositis), a reddish or purplish rash may appear around the eyes, neck, upper chest, elbows, or knees.

Dermatomyositis is a muscle inflammation associated with the skin problem that can be read here: Dermatomyositis

Diagnosis

Management

There is currently no cure for polymyositis, but treatment aims to manage symptoms and reduce inflammation. The type of therapy provided depends on the patient's symptoms, age, health status, and the severity of the disease.

Medications

Doctors may prescribe anti-inflammatory medications like corticosteroids. The most commonly used corticosteroids are prednisone and methylprednisolone. If patients do not respond to these medications or experience severe side effects, doctors may prescribe immunomodulators, a class of drugs that help activate and restore normal immune function. These medications are intended to help the patient's body fight the disease.

Non-Pharmacological Therapy

This disease usually requires evaluation by multiple specialists, especially if muscle weakness has affected various organs. Physical therapy can be performed on affected muscles to prevent further muscle wasting. Additionally, patients are typically advised to engage in exercise to improve muscle strength under the supervision of trained personnel. A diet high in protein may also be recommended to aid in muscle building.

Complications

Polymyositis can lead to severe complications, such as:

• Digestive tract issues

Polymyositis can also affect digestive tract muscles, leading to malnutrition and weight loss. The disease may also impair the swallowing process.

• Respiratory failure

The disease can also attack the respiratory muscles. Initially, patients may experience difficulty breathing. If not promptly addressed, this could lead to respiratory failure.

• Aspiration pneumonia

Polymyositis can cause swallowing difficulties, known as dysphagia. This may cause food to enter the respiratory tract, leading to pneumonia.

Prevention

Currently, there is no known way to prevent polymyositis because the exact cause is not well understood. The disease can relapse if treatment is stopped without a doctor's approval. Medications like steroids generally need to be tapered off gradually and cannot be stopped abruptly. Avoid discontinuing therapy without your doctor's consent.

When to See a Doctor?

If you experience muscle weakness or symptoms of polymyositis as described above, you should seek medical treatment to prevent the disease from worsening. The earlier treatment is initiated, the better the outcomes. If you experience breathing difficulties or trouble swallowing, seek emergency medical attention for prompt care.

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