POLYMYOSITIS

Polymyositis is a rare autoimmune disease that affects the muscles, causing inflammation and weakness. This autoimmune disease falls under the category of inflammatory myopathies, which are conditions that inflame the muscles involved in movement. This inflammation not only affects the muscles but also harms nearby tissues like blood vessels that supply essential oxygen and nutrients to the muscles.

Polymyositis targets muscles in the thighs and upper arms, resulting in muscle weakness and discomfort on both sides of the body. Everyday tasks like climbing stairs or standing up from a chair become challenging due to this muscle weakness. Although there isn’t a cure for polymyositis, there are treatments available to alleviate its symptoms.

Causes of polymyositis

The exact cause of polymyositis remains unknown, but research suggests it may be linked to autoimmune dysfunction. In autoimmune disorders, the body’s defense mechanism, which typically defends against foreign invaders like viruses, mistakenly attacks its tissues. There’s also a possibility that polymyositis could be inherited, meaning it’s passed down through families.

Comparison with dermatomyositis

Polymyositis is closely linked to another inflammatory condition known as dermatomyositis. Both conditions exhibit similar symptoms of muscle weakness and soreness. However, dermatomyositis stands out as it also presents with a rash. This rash may appear smooth or scaly and might not necessarily develop near the affected muscles. Additionally, dermatomyositis could cause swelling around the eyes or fingernails.

Comparison with polymyalgia rheumatica

Polymyositis shares several symptoms with another condition called polymyalgia rheumatica. Both disorders affect muscles on both sides of the body, particularly around the abdomen area. The primary distinction lies in their symptoms: polymyalgia rheumatica mainly induces muscle pain and stiffness, whereas polymyositis primarily results in weakness alongside pain.

Prevalence

Polymyositis is considered a rare disease, with an estimated annual incidence of 1-8 cases per million individuals worldwide. It most commonly affects adults between the ages of 30 and 60, but it can occur at any age. It’s exceptionally rare in children and tends to affect women more frequently than men.

Symptoms of polymyositis

Polymyositis manifests due to inflammation, which causes irritation and swelling in the muscles. The resulting muscle weakness typically affects both sides of the body and tends to impact muscle groups closer to the body’s core, including the hips, shoulders, thighs, upper arms, upper back, and neck. Other symptoms may include:

Fatigue
Difficulty swallowing (dysphagia)
Muscle pain and tenderness
Difficulty rising from a seated position
Difficulty climbing stairs
Difficulty breathing
Joint pain and stiffness
Fever
Weight loss

The progression of the condition is gradual throughout 3 to 6 months. However, there are instances of a rare, rapid onset of polymyositis.

This autoimmune disease can enter periods of inactivity, where symptoms diminish or disappear entirely. During these inactive phases, individuals may feel well and experience few or no symptoms.

Risk Factors

While the exact risk factors for this autoimmune disease are not well-defined, certain factors may increase the likelihood of developing the condition, including:

Gender: Women are slightly more likely to develop polymyositis than men.
Age: It most commonly affects adults between the ages of 30 and 60.
Family history: Having a family member with an autoimmune disease may increase the risk.
Environmental factors: Exposure to certain environmental triggers, such as infections or medications, may play a role.
Having other autoimmune conditions such as lupus, rheumatoid arthritis, scleroderma, or Sjogren’s syndrome. Additionally, individuals with HIV or AIDS are at a higher risk of polymyositis.

Diagnosing polymyositis

Diagnosing this autoimmune disease can be challenging as there are no straightforward tests for it. It often requires time and a thorough examination by doctors to confirm the condition.

Your doctor will begin by taking your medical history to rule out other possible conditions. They may also assess your muscle strength through various tests.

Additional tests you may undergo include:

Blood tests: Blood tests (such as creatine kinase levels tests) help doctors identify signs of muscle damage by examining certain markers in your blood.
EMG (electromyography): This diagnostic procedure evaluates the electrical impulses in your muscles to determine if they exhibit normal patterns or abnormalities.
MRI (magnetic resonance imaging): Using a magnet, MRI scans create detailed images of large muscle areas, assisting in identifying any abnormalities or inflammation.
Muscle biopsy: In this procedure, a small sample of muscle tissue is collected for testing to assess for signs of inflammation and other abnormalities.

These diagnostic tests, combined with a comprehensive medical evaluation, aid doctors in confirming a diagnosis of polymyositis.

Treatments for polymyositis

Polymyositis is a chronic condition, meaning it persists over time once diagnosed. However, there are strategies available to help manage its symptoms effectively.

Medications for Polymyositis:

Corticosteroids: These are often the initial medications prescribed to alleviate symptoms of polymyositis. Corticosteroids work by reducing inflammation and relieving pain associated with the condition.
Immunosuppressants: Another category of medications used in treating polymyositis is immunosuppressants. These drugs help suppress the immune system’s overactivity, which is responsible for attacking the body’s own tissues. Examples include azathioprine (Imuran® and Azasan®), methotrexate (Rheumatrex® and Trexall®), and rituximab (Rituxan).

Therapeutic Treatments:

In addition to medication, your doctor may recommend the following therapies based on your specific symptoms:

Physical Therapy: A physical therapist can design exercises tailored to your needs, aiming to improve muscle strength and mobility.
Speech Therapy: Polymyositis may weaken the muscles used for speech, leading to difficulties in pronunciation. Speech therapy can assist in enhancing clarity and articulation.
Dietetic Assessment: Muscle weakness over time can affect chewing and swallowing. A nutritionist or registered dietitian can help devise a soft and nutritious meal plan to address these challenges.

Other Treatment Options:

Some individuals with polymyositis may benefit from additional treatments such as:

Regular blood infusions: This involves administering antibodies called immunoglobulins via intravenous (IV) infusion to bolster the body’s immune response and protect muscles from autoimmune attacks.
Assistive Devices: Braces and other specialized devices may be recommended to aid individuals experiencing difficulty in movement.

Home Care Tips

In addition to medical treatment, there are several home care tips that individuals with this autoimmune disease can follow to manage their symptoms:

Pace yourself: Avoid overexertion and take regular breaks to rest.
Maintain a healthy diet: Eat a balanced diet rich in fruits, vegetables, whole grains, and lean proteins to support muscle health.
Stay active: Engage in gentle exercises, such as walking or swimming, to maintain muscle strength and flexibility.
Seek support: Joining a support group or seeking counseling can provide emotional support and practical tips for coping with the challenges of living with polymyositis.

Prevention

Since the exact cause of polymyositis is unknown, it is challenging to prevent its onset. However, avoiding known risk factors, such as infections or certain medications, may help reduce the risk of developing the condition.

Complications of Polymyositis

Polymyositis can lead to several complications, including:

Difficulty Swallowing: This can occur if the muscles in the esophagus are affected, resulting in weight loss and malnutrition.
Aspiration Pneumonia: Difficulty swallowing increases the risk of inhaling food or liquid into the lungs, potentially causing pneumonia.
Breathing Problems: If chest muscles are affected, individuals may experience shortness of breath and, in severe cases, respiratory failure.
Digestive Issues: Weakened muscles in the digestive tract may cause difficulties in digesting food, leading to malnutrition.
Falls: Weak muscles increase the risk of falls and subsequent bone fractures.

Additionally,this autoimmune disease is associated with other health conditions, although it doesn’t necessarily cause them. These include heart disease, lung disease, cancer, and other connective tissue disorders like lupus or rheumatoid arthritis.

When to See a Doctor

It is essential to consult a doctor if you experience persistent muscle weakness, pain, or difficulty performing everyday tasks. Early diagnosis and treatment can help manage symptoms and prevent complications.

Outlook/Prognosis

The prognosis for polymyositis varies depending on the severity of the disease and how well it responds to treatment. With prompt diagnosis and appropriate management, many individuals with polymyositis can experience significant improvement in their symptoms and quality of life.

Sources

National Institute of Neurological Disorders and Stroke. (n.d.). Polymyositis Information Page.
Cedars-Sinai. Polymyositis and Dermatomyositis.
Johns Hopkins Medicine. Polymyositis.
StatPearls. Polymyositis.
Arthritis Foundation. Myositis.
Muscular Dystrophy Association. Polymyositis.
Genetic and Rare Diseases Information Center. Polymyositis.
Annals of the Rheumatic Diseases. Polymyositis, not polymyalgia rheumatica.
National Organization for Rare Diseases. Polymyositis
Myositis Association. Polymyositis
Brigham and Women’s Hospital. Inflammatory Diseases of the Muscle
Mayo Clinic. Polymyositis.