Polymyositis

What is Polymyositis?

Idiopathic inflammatory myopathies are conditions that cause inflammation and weakness in muscles for unknown reasons. There are four main types: polymyositis, dermatomyositis, inclusion body myositis, and necrotizing myopathy. These were further divided into 7 classes by Bohan and Peter.

Polymyositis is a type of autoimmune disease that involves long-term inflammation and is identified by widespread muscle weakness. It targets the interior layer of muscles, unlike dermatomyositis which affects the outer layer of muscles along with causing skin problems.

Polymyositis gradually develops over months, whereas inclusion body myositis (IBM), progresses slowly in older people over a period of months to years and has more severe symptoms. IBM may result from an autoimmune reaction (where the body attacks its own cells) or a long-lasting viral infection such as the human T-cell leukemia type 1 (HTLV-1).

As an autoimmune disorder, polymyositis falls under rheumatological diseases and requires long-term treatments with steroids or “immunomodulators” – drugs that help regulate the immune system. Treatment also focuses on addressing the underlying causes.

Polymyositis is a rare disorder but needs to be considered when patients show unexplained muscle weakness. Failure to diagnose can significantly impact the patient’s quality of life because it can lead to serious complications.

What Causes Polymyositis?

Polymyositis (PM), an immune system disorder, develops due to an unusual activation of immune cells called cytotoxic T lymphocytes (CD8 cells) and macrophages against proteins found in muscles. This strong immune response causes damage to certain parts of skeletal muscles leading to PM.

Different proteins, called cytokines, play a key role in causing a severe muscle disorder called rhabdomyolysis. This disorder often affects people who are already suffering from some type of systemic disease due to viruses, cancers, or other immune system disorders. Viruses like HIV, HTLV1, and hepatitis C often cause polymyositis. They do this by causing damage and swelling in the muscle cells and creating lumps.

Coxsackievirus is another cause of polymyositis. It does this by interfering with the functioning of a specific group of proteins, called the major histocompatibility complex (MHC). Damage to the inner lining and the wall of blood vessels leads to the release of cytokines, further causing PM.

An important factor that triggers PM-inducing rhabdomyolysis is underlying cancer like lung cancer, genitourinary cancer, lymphomas and others. If a person has polymyositis, there is an increased chance of cancer developing 2-5 years after the diagnosis, specifically non-Hodgkin lymphoma. It has the highest risk of development, followed by lung cancer and bladder cancer.

Other causes include certain genetic factors (A1, B8, DR3), autoimmune diseases such as celiac disease, and the use of certain medications like hydralazine, procainamide, antiepileptics, and angiotensin-converting enzyme (ACE) inhibitors. These medications can sometimes act as triggers. There have been rare cases of patients on statin therapy (used to lower cholesterol levels) developing polymyositis.

Risk Factors and Frequency for Polymyositis

Autoimmune disorders are a leading cause of death among middle-aged people in the United States. They vary in how common they are. Specifically, polymyositis is an autoimmune disease that typically impacts people over the age of 20 and is rarely seen in children. On the other hand, dermatomyositis, another autoimmune disease, affects people either between the ages of 5-15 or 45-60.

Women are about twice as likely to develop these diseases as men, which is the opposite of what is seen with the autoimmune disease known as IBM.
In the United States, between 0.5-8.4 per 100,000 people will develop these autoimmune disorders.
These diseases are more commonly reported in Black individuals than in White individuals.

Signs and Symptoms of Polymyositis

Polymyositis diagnosis can be tough, particularly in the early stages, due to the lack of visible skin symptoms, which you’d typically find in a related condition known as dermatomyositis. The condition is usually diagnosed through a detail patient’s history including family history, medication history, and any preceding infections. Important clues to help confirm the condition include:

Gradual building up muscle weakness, sometimes coupled with muscle ache
Joint pains which might indicate other autoimmune issues
Problems in standing from a sitting position or difficulty in doing activities that involve upper body movements like combing hair or holding the neck upright. This is because polymyositis often affects the pelvic muscles more than the shoulder muscles

Patients could also report difficulty in swallowing due to muscle involvement in the throat or food pipe, difficulty in breathing, or chest discomfort due to effects on their heart muscles or pericardium, which is the layer covering their heart.

Typical characteristics of polymyositis are a gradual yet progressive disease impacting evenly the muscles around the body mid-section or the neck that can sometimes be painful. Common complaints include inability to lift arms overhead or to rise from a sitting position. As the disease progresses to distal muscles (those further away from the center of the body), it can affect fine movements like writing or playing music. It might also come with mild fever, loss of appetite, joint pain and weight loss. In some patients, polymyositis can affect the lungs causing shortness of breath and a dry cough, bring about chest discomfort and difficulty breathing due to restrictive cardiomyopathy, cause constipation or bloating because of gastrointestinal involvement, and fingers may tighten and change color due to a condition known as Raynaud’s phenomenon.

During a physical exam, a complete motor and sensory examination of the affected muscles is a must. Although sensory examinations often appear normal, motor examination might show a decrease in power or muscle strength in the parts affected, depending upon the severity of the disease. In severe cases, patients might lose their reflexes. Some patients may have limited movement of muscles in the trunk of their body, resulting in abnormal bending, a condition known as camptocormia. Furthermore, if polymyositis affects the muscles in the nasal and throat area, it may lead to a nasal-toned speech. If the condition is associated with an underlying cancer, specific symptoms related to that particular cancer may also be visible.

Testing for Polymyositis

If your doctor thinks you might have polymyositis, a condition which causes muscle inflammation, they will use a variety of tests to make a diagnosis. These can include blood tests, muscle tests, biopsies, imaging studies, and a range of other evaluations.

A complete blood count (CBC) can reveal an increased number of lymphocytes, a type of white blood cell, in many patients with polymyositis. This test may also show a high amount of platelets, or thrombocytosis. The erythrocyte sedimentation rate (ESR), which measures inflammation levels in your body, may also be elevated. Another blood test checks for levels of serum creatine kinase (CK), an enzyme that can signal muscle damage when present at high levels — up to 50 times the normal range.

Your doctor may also check for increased levels of antibodies in your blood. One of these, antinuclear antibody (ANA), can be seen in around 33 percent of the patients with polymyositis. If this is positive, additional specific antibody tests may be done such as anti-signal recognition particle (SRP) and anti-aminoacyl tRNA synthetases (ARS).

Another step in diagnosing polymyositis often involves electromyography (EMG), a test that measures muscle activity. Almost all patients with polymyositis will show abnormal results on this test due to changes in levels of electrical activity in the muscles. Using a biopsy in concert with either EMG or magnetic resonance imaging (MRI) can give a more definitive diagnosis. The biopsy will show infiltrates of certain immune cells and areas of muscle necrosis, or cell death.

Imaging studies like MRI, computed tomography (CT) scans, or ultrasounds can help doctors pinpoint the areas of muscle damage and check for any underlying cancers. MRI is particularly important for this purpose. If you have trouble swallowing, a barium swallow test may be performed. Additional testing may be done on the lungs and heart if symptoms suggest involvement of these systems.

Treatment Options for Polymyositis

Polymyositis, a type of inflammatory muscle disease, can be treated through a combination of medicine and other non-drug treatments. The most common initial treatment involves steroids, such as Prednisone and methylprednisolone. These steroids help to reduce inflammation, but they need to be reduced slowly over time rather than stopped abruptly.

If steroids aren’t effective or cause severe side effects, doctors may turn to immune modulating drugs, like methotrexate, azathioprine and cyclosporine. These work by regulating the immune system, which can be overactive in polymyositis. A drug called cyclophosphamide can be particularly effective for those patients whose lung tissue is affected by the disease.

Another treatment option for people with long-term, unresponsive polymyositis is intravenous immunoglobulins (IVIG), or proteins that help your body fight off infections. Studies have shown that around 70% of patients see an improvement after using IVIG. It can also significantly improve those with swallowing problems due to the disease’s impact on the esophagus.

In certain cases where the disease is resistant to other treatments, biologic drugs, like infliximab and etanercept, may be used. There are also other treatments, such as tacrolimus, mycophenolate mofetil and rituximab, that have proved beneficial for patients that haven’t responded to other treatments.

Importantly, patients should also receive evaluation and care from specialists relevant to their symptoms—like a cardiologist for heart complications, a lung specialist for lung complications, and a speech therapist for changes in voice.

Non-drug treatments are also important. Physical therapy can help prevent muscle weakness due to lack of use. Doctors often recommend that these patients do supervised strength training exercises. It’s also generally recommended that these individuals consume a protein-rich diet, which can help strengthen their muscles.

When a patient shows signs of myopathy, which is a muscle disease that weakens the muscles, doctors have to rule out other conditions to make sure they’re treating the right problem. These conditions can include:

A myopathy caused by an imbalance of certain minerals in the body, like potassium, phosphate, or magnesium. This kind of imbalance can cause muscle cramps and aches that are very similar to Polymyositis (PM).
Endocrine disorders, such as hypothyroidism, hyperthyroidism, diabetes mellitus, metabolic syndrome, etc. These conditions can make the muscles close to the center of the body, also known as the proximal muscles, weak.

Also, doctors should rule out other immune system disorders to diagnose polymyositis. These disorders can include:

Dermatomyositis, which usually shows up as skin conditions and changes in muscle tissues.
Myasthenia gravis, mixed connective tissue disorder, systemic lupus erythematosus (SLE), scleroderma, and myositis, which cause muscle inflammation.
Illnesses caused by medications or treatment, such as steroid-induced myopathy or Cushing syndrome.
Conditions where muscular pain and weakness are common symptoms, like fibromyalgia or polymyalgia rheumatica.

Amyotrophic lateral sclerosis (ALS), which also causes myopathy, should also be ruled out. Also, it’s important to check on the medications the patient is using because some drugs can cause myopathy. These drugs can include statins, alcohol derivatives like ethanol, antimetabolites such as vincristine, azathioprine, chloroquine/primaquine, and antifungal agents.

What to expect with Polymyositis

Polymyositis is a long-term condition that can have a serious impact over time. Besides causing disability and affecting a person’s quality of life, this disease is also linked to a 10% mortality rate, particularly in those who develop heart problems or cancer. Most patients typically respond to treatment with steroids.

Polymyositis prognosis is especially poor for patients who have a resistant (“refractory”) form of the disease, older women, Black people, and individuals with the disease spreading throughout the body (“systematic involvement”).

Possible Complications When Diagnosed with Polymyositis

Polymyositis is a rare disease that can lead to serious health problems and even death due to related conditions, such as problems with big blood vessels or the digestive system. People with polymyositis have a slightly higher risk (about 2.2%) of having a heart attack compared to the general population. In the first year after a diagnosis of polymyositis, people are more likely to be diagnosed with cancer. This is why doctors should check for cancer in all patients with this disease, especially older patients and women. A study showed that older patients with a high ratio of certain types of white blood cells were more likely to develop lung cancer, bladder cancer or a type of blood cancer called non-Hodgkin lymphoma.

Polymyositis can affect the muscles in the lower part of the esophagus and, in advanced stages of the disease, up to 70% of patients may have trouble swallowing or may experience regurgitation. This can lead to a lung infection called aspiration pneumonia. Lung problems can increase the mortality rate and greatly affect the quality of life. Polymyositis can also lead to loss of pregnancy in young women with active disease.

Polymyositis can trigger a condition where the blood clots too easily, leading to a higher chance of blood clots in the bloodstream. Some studies also suggest that people with polymyositis may be more likely to develop a nerve disease called amyotrophic lateral sclerosis and a bone disease called osteoporosis.

Health Risks Associated with Polymyositis:

Increased risk of heart attack
Higher likelihood of being diagnosed with cancer in the first year after polymyositis diagnosis
Difficulty swallowing and regurgitation due to esophageal muscle problems
Chances of aspiration pneumonia (lung infection)
Chances of pregnancy loss in women of child-bearing age
Elevated risk of blood clots
Potential increased risk of developing nerve disease (amyotrophic lateral sclerosis)
Greater risk of osteoporosis (bone weakness)

Preventing Polymyositis

Polymyositis is a disease that can cause several other health conditions, so it’s crucial for patients to manage their health in the right way to reduce any additional discomfort. Here are some important things patients should keep in mind to prevent complications in the future:

1. Patients should try to avoid extremely cold weather. This is because the cold can increase the risk of Raynaud’s phenomenon – a condition that causes certain parts of the body, like the fingers and toes, to temporarily lose blood flow and become numb when exposed to cold temperatures or stress. As a result, the body parts affected by Raynaud’s can develop tissue death due to the lack of blood flow.

2. Those who have a condition called ‘esophageal motility disorder’ – where muscles in the esophagus (the tube connecting the throat to the stomach) don’t work properly making it hard to swallow – should avoid lying down right after eating meals.

3. Supplements which contain calcium and vitamin D should be taken early on to avoid disease or bone weakening caused by certain medicines like steroids.

4. If there’s a chance the patient might have a hidden cancer – especially in patients who are older men with wide-ranging symptoms – detailed information should be shared.

In addition to these tips, it’s necessary to stress on the importance of regular physical exercise.

Frequently asked questions

The prognosis for Polymyositis can vary depending on certain factors. However, it is generally considered a long-term condition that can have a serious impact over time. Some key points about the prognosis include: - Polymyositis is linked to a 10% mortality rate, particularly in those who develop heart problems or cancer. - Most patients typically respond to treatment with steroids. - The prognosis is especially poor for patients who have a resistant ("refractory") form of the disease, older women, Black people, and individuals with the disease spreading throughout the body ("systematic involvement").

Polymyositis can be caused by an unusual activation of immune cells called cytotoxic T lymphocytes (CD8 cells) and macrophages against proteins found in muscles. It can also be caused by viruses like HIV, HTLV1, hepatitis C, and Coxsackievirus, which cause damage and swelling in the muscle cells. Underlying cancers like lung cancer, genitourinary cancer, and lymphomas can also trigger polymyositis. Additionally, certain genetic factors, autoimmune diseases, and the use of certain medications can contribute to the development of polymyositis.

Signs and symptoms of Polymyositis include: - Gradual building up muscle weakness, sometimes coupled with muscle ache - Joint pains which might indicate other autoimmune issues - Problems in standing from a sitting position or difficulty in doing activities that involve upper body movements like combing hair or holding the neck upright. This is because polymyositis often affects the pelvic muscles more than the shoulder muscles - Difficulty in swallowing due to muscle involvement in the throat or food pipe - Difficulty in breathing or chest discomfort due to effects on the heart muscles or pericardium - Gradual yet progressive disease impacting evenly the muscles around the body mid-section or the neck that can sometimes be painful - Inability to lift arms overhead or to rise from a sitting position - Impact on fine movements like writing or playing music as the disease progresses to distal muscles - Mild fever, loss of appetite, joint pain, and weight loss - Shortness of breath and a dry cough if the lungs are affected - Chest discomfort and difficulty breathing due to restrictive cardiomyopathy - Constipation or bloating because of gastrointestinal involvement - Fingers tightening and changing color due to Raynaud's phenomenon - Abnormal bending of the trunk of the body, known as camptocormia, in severe cases - Nasal-toned speech if the muscles in the nasal and throat area are affected - Specific symptoms related to an underlying cancer if the condition is associated with it.

The types of tests that are needed for Polymyositis include: - Blood tests: complete blood count (CBC), erythrocyte sedimentation rate (ESR), serum creatine kinase (CK), and antibody tests (such as antinuclear antibody (ANA), anti-signal recognition particle (SRP), and anti-aminoacyl tRNA synthetases (ARS)). - Muscle tests: electromyography (EMG) to measure muscle activity. - Biopsies: to examine muscle tissue for immune cell infiltrates and areas of muscle necrosis. - Imaging studies: MRI, CT scans, ultrasounds to pinpoint areas of muscle damage and check for underlying cancers. - Additional tests may be done on the lungs, heart, and swallowing function if symptoms suggest involvement of these systems.

A doctor needs to rule out the following conditions when diagnosing Polymyositis: - A myopathy caused by an imbalance of certain minerals in the body, like potassium, phosphate, or magnesium. - Endocrine disorders, such as hypothyroidism, hyperthyroidism, diabetes mellitus, metabolic syndrome, etc. - Dermatomyositis, which usually shows up as skin conditions and changes in muscle tissues. - Myasthenia gravis, mixed connective tissue disorder, systemic lupus erythematosus (SLE), scleroderma, and myositis, which cause muscle inflammation. - Illnesses caused by medications or treatment, such as steroid-induced myopathy or Cushing syndrome. - Conditions where muscular pain and weakness are common symptoms, like fibromyalgia or polymyalgia rheumatica. - Amyotrophic lateral sclerosis (ALS). - Medications that can cause myopathy, such as statins, alcohol derivatives like ethanol, antimetabolites such as vincristine, azathioprine, chloroquine/primaquine, and antifungal agents.

When treating Polymyositis, the side effects of the medications used can vary. However, some common side effects of the medications used to treat Polymyositis include: - Steroids (such as Prednisone and methylprednisolone): These can cause side effects such as weight gain, mood changes, increased appetite, and increased risk of infections. - Immune modulating drugs (such as methotrexate, azathioprine, and cyclosporine): These can cause side effects such as nausea, vomiting, liver problems, and increased risk of infections. - Cyclophosphamide: This drug can cause side effects such as nausea, vomiting, hair loss, and increased risk of infections. - Intravenous immunoglobulins (IVIG): Side effects of IVIG can include headache, fever, chills, and allergic reactions. - Biologic drugs (such as infliximab and etanercept): These drugs can cause side effects such as injection site reactions, increased risk of infections, and allergic reactions. - Other treatments (such as tacrolimus, mycophenolate mofetil, and rituximab): Side effects of these treatments can vary, but may include nausea, vomiting, increased risk of infections, and allergic reactions. It's important to note that the benefits of these treatments generally outweigh the potential side effects, and the specific side effects experienced can vary from person to person. It's important for patients to discuss any concerns or potential side effects with their healthcare provider.

Rheumatologist

Between 0.5-8.4 per 100,000 people will develop polymyositis in the United States.

Polymyositis can be treated through a combination of medicine and other non-drug treatments. The most common initial treatment involves steroids, such as Prednisone and methylprednisolone, to reduce inflammation. If steroids are not effective or cause severe side effects, immune modulating drugs like methotrexate, azathioprine, and cyclosporine may be used. Intravenous immunoglobulins (IVIG) can be an option for long-term, unresponsive cases, and biologic drugs like infliximab and etanercept may be used in resistant cases. Other treatments like tacrolimus, mycophenolate mofetil, and rituximab have also shown benefits. Additionally, non-drug treatments like physical therapy and a protein-rich diet are important.

Polymyositis is a type of autoimmune disease that involves long-term inflammation and widespread muscle weakness. It targets the interior layer of muscles and requires long-term treatment with steroids or immunomodulators.