Polymyositis

Polymyositis is a rare, long-term (chronic) disease where your body's immune system mistakenly attacks and inflames your muscles. This leads to muscle weakness, especially in the muscles closest to your body's center, like those in your hips, thighs, shoulders, and neck. While there's no cure, treatments can help manage symptoms and improve muscle strength.

What is Polymyositis?

Polymyositis is a rare, chronic inflammatory disease where your immune system mistakenly attacks your healthy muscle tissue. This causes progressive muscle weakness, particularly in the muscles closest to your body's trunk, such as those in your hips, thighs, shoulders, and neck. It can make everyday activities challenging.

Polymyositis means "inflammation of many muscles." It is one of a group of conditions called inflammatory myopathies. In polymyositis, the inflammation leads to damage of the muscle fibers, making them weaker over time. This weakness usually affects both sides of your body equally. The condition is considered an autoimmune disease. This means your body's natural defense system, which normally fights off germs and infections, mistakenly targets your own healthy cells. In this case, it attacks muscle cells. While polymyositis can affect anyone, it most often appears in adults between the ages of 30 and 60. It is also more common in women than in men. The disease is chronic, meaning it is a long-term condition that requires ongoing management.

Symptoms

The main symptom of polymyositis is gradual, progressive muscle weakness, typically affecting muscles close to the body's center, like those in the hips, thighs, shoulders, and neck. This weakness can make everyday tasks difficult, such as climbing stairs, standing up from a chair, or lifting objects.

The muscle weakness associated with polymyositis develops slowly, often over weeks or months, rather than suddenly. You might first notice difficulty with activities that use your large muscles. For example, you may find it harder to lift your arms above your head or to get out of a low chair. Beyond weakness, some people with polymyositis may experience other symptoms. These can include fatigue, which is a feeling of extreme tiredness, and sometimes mild muscle pain or tenderness. However, muscle pain is less common than the weakness itself. In some cases, polymyositis can affect muscles involved in swallowing (dysphagia), leading to problems eating or drinking. It can also affect the voice or, rarely, lead to shortness of breath if the muscles used for breathing are weakened.

Causes & risk factors

Polymyositis is an autoimmune disease, meaning your immune system mistakenly attacks your own muscle tissues. The exact reason this happens is unknown, but certain factors can increase your risk. These include being female and typically being between 30 and 60 years old when symptoms begin.

The primary cause of polymyositis is an autoimmune response. For reasons not fully understood, the immune system, which usually protects the body from foreign invaders like bacteria and viruses, begins to attack healthy muscle fibers. This attack leads to inflammation and damage within the muscles. While the specific trigger for this autoimmune attack is unknown, several factors are associated with an increased risk of developing polymyositis. Women are more likely to develop the condition than men. The disease most commonly affects adults, usually appearing between the ages of 30 and 60. Polymyositis can also occur alongside other autoimmune diseases, such as lupus or rheumatoid arthritis. In some instances, it may be linked to certain types of cancer, particularly in older adults. However, it's important to note that these are associations, and not everyone with polymyositis will have these other conditions.

How it's diagnosed

Diagnosing polymyositis involves several tests to confirm muscle inflammation and rule out other conditions. A doctor will typically start with a physical exam and blood tests to check for elevated muscle enzymes and specific antibodies. Further tests, like electromyography, MRI, and a muscle biopsy, help confirm the diagnosis.

The diagnostic process for polymyositis often begins with a thorough physical examination. Your doctor will assess your muscle strength and look for signs of weakness, especially in your hips, thighs, shoulders, and neck. They will also ask about your symptoms and medical history. Blood tests are crucial for diagnosis. These tests check for high levels of muscle enzymes, such as creatine kinase (CK), which are released into the bloodstream when muscle tissue is damaged. Blood tests can also identify certain autoantibodies, which are proteins produced by the immune system that mistakenly target the body's own tissues. Other tests may include electromyography (EMG), which measures the electrical activity of muscles and nerves, and magnetic resonance imaging (MRI), which can show areas of muscle inflammation. The most definitive test is often a muscle biopsy, where a small sample of muscle tissue is removed and examined under a microscope to look for signs of inflammation and damage.

Treatment options

Treatment for polymyositis aims to reduce muscle inflammation, improve muscle strength, and manage symptoms. Corticosteroids, like prednisone, are usually the first-line treatment to suppress the immune system. Immunosuppressant medications are often added to reduce the need for high-dose steroids and provide long-term control of the disease.

The primary goal of treatment is to control the inflammation and prevent further muscle damage. Corticosteroids, such as prednisone, are commonly prescribed first. These medications work by suppressing the overactive immune system, which helps to reduce inflammation in the muscles. To minimize the long-term side effects of corticosteroids, doctors often add other immunosuppressant medications. These can include drugs like azathioprine, methotrexate, or mycophenolate mofetil. These medications also help to calm the immune system and can be used to maintain symptom control over time. In some cases, other treatments may be used. Intravenous immunoglobulin (IVIG) involves receiving healthy antibodies through a vein, which can help block the harmful antibodies attacking your muscles. Physical therapy is also a vital part of treatment, helping to maintain and improve muscle strength, flexibility, and function. Occupational therapy can help you learn new ways to perform daily tasks, and speech therapy may be needed if swallowing muscles are affected.

Recovery & outlook

Polymyositis is a chronic condition, meaning it is long-term, but treatment can significantly improve muscle strength and overall quality of life. While there is no cure, many people achieve good control of their symptoms and can lead active lives. Some may experience ongoing muscle weakness or require continuous treatment.

With appropriate and consistent treatment, many individuals with polymyositis experience a significant improvement in their muscle strength and a reduction in symptoms. Early diagnosis and treatment are often associated with better outcomes. The goal is to manage the disease and prevent its progression. Recovery can be a gradual process, and it often involves a combination of medication and physical therapy. While some people may achieve near-normal muscle function, others might experience some residual muscle weakness or fatigue, even with treatment. This is why ongoing monitoring by a healthcare team is important. The outlook for polymyositis varies from person to person. Factors like the severity of the disease at diagnosis, how well a person responds to treatment, and whether other organs are affected can influence the long-term outcome. Most people with polymyositis can manage their condition and maintain a good quality of life with ongoing medical care.

When to see a doctor

You should see a doctor if you develop new or worsening muscle weakness that affects your daily activities, especially if it's in your hips, thighs, shoulders, or neck. Seek immediate medical attention if you experience sudden difficulty swallowing, severe shortness of breath, or any other rapid decline in muscle function.

It is important to consult a healthcare provider if you notice any persistent or progressive muscle weakness. This includes difficulty with tasks like climbing stairs, getting up from a seated position, lifting objects, or raising your arms. Early diagnosis and treatment can significantly improve the outcome of polymyositis. If you have already been diagnosed with polymyositis, you should contact your doctor if your symptoms worsen or if you develop new symptoms. This could indicate a need to adjust your treatment plan. Do not change your medications or dosages without consulting your doctor. Seek emergency medical care if you experience severe or sudden symptoms. These include significant trouble swallowing that makes eating or drinking difficult, or new or worsening shortness of breath. These symptoms could indicate a more serious complication requiring immediate attention.

Frequently asked questions

Is polymyositis contagious?

No, polymyositis is not contagious. It is an autoimmune disease, meaning it results from your body's immune system mistakenly attacking its own tissues, not from an infection that can spread from person to person.

Can polymyositis be cured?

Currently, there is no cure for polymyositis. However, treatments are very effective in managing symptoms, reducing muscle inflammation, and improving muscle strength and function. Many people can achieve good control of their condition with ongoing medical care.

What is the difference between polymyositis and dermatomyositis?

Both polymyositis and dermatomyositis are inflammatory muscle diseases. The key difference is that dermatomyositis also involves a characteristic skin rash, which is not present in polymyositis. Both conditions cause muscle weakness, but dermatomyositis has distinct skin symptoms.

Does polymyositis affect children?

While polymyositis primarily affects adults, a similar condition called juvenile polymyositis can occur in children. However, inflammatory muscle diseases in children are more commonly dermatomyositis. If a child shows symptoms of muscle weakness, a doctor should evaluate them.

Can diet help manage polymyositis?

While no specific diet can cure polymyositis, eating a balanced, nutritious diet is important for overall health and can help manage symptoms like fatigue. If you are taking corticosteroids, your doctor might recommend a diet to help manage potential side effects, such as bone thinning or weight gain.

How does polymyositis affect daily life?

Polymyositis can affect daily life by causing muscle weakness that makes routine tasks difficult, such as walking, lifting, or even swallowing. However, with effective treatment and therapies like physical and occupational therapy, many individuals can significantly improve their function and maintain an active lifestyle.

Sources

• MedlinePlus — Polymyositis
• Mayo Clinic — Polymyositis
• Cochrane Library — Polymyositis