Mya Care Blogger 11 Oct 2023

Myositis is a general term that means inflammation of the muscles. It refers to several autoimmune muscle diseases that can cause muscle weakness, pain, and sometimes skin rashes. There are different types of myositis, each with its own causes, symptoms, and treatments.

In this article, we will explore what myositis is, how it affects the body, and what you can do to manage it.

What is Myositis?

Myositis is a rare disease that affects the muscles. It is an autoimmune condition that results from a dysfunctional immune system that attacks muscle fibers, causing chronic inflammation and damage. The inflammation can interfere with the ability of the muscles to contract, leading to weakness and fatigue. Myositis may also be called idiopathic inflammatory myositis or autoimmune myopathy.

This rare muscle disease is thought to affect between 5 - 22 people per 100,000. It is more common in females, with the exception of inclusion body myositis, which affects men more on average

There are 5 types of myositis[1]:

  • Polymyositis is the most common type. It affects multiple muscles, usually in the trunk, shoulders, hips, and thighs, as well as muscles that control breathing and swallowing in some cases.
  • Dermatomyositis is similar to polymyositis, yet it also presents with skin rashes and other skin-related symptoms. It affects both adults and children.
  • Inclusion body myositis is the most common autoimmune myopathy that affects people over 50 years old. It causes muscle weakness in the wrists, fingers, lower legs, feet, and sometimes in the facial muscles and throat. It is more common in men than women.
  • Juvenile myositis affects children under 18 years old and resembles dermatomyositis.
  • Necrotizing Myopathy is a newer form of myositis characterized by less muscle inflammation and signs of muscle necrosis or death. It is not distinguishable from polymyositis without proper testing.[2]

Myositis Symptoms

The main symptom of myositis is muscle weakness and fatigue in the muscles near the torso, such as the upper arms and thighs. It is challenging to carry out regular tasks, including walking, climbing stairs, lifting goods, or reaching aloft, due to the weakness of these muscles. It may be gradual or sudden and may affect one or more parts of the body.[3]

Other symptoms of myositis may include:

  • Muscle pain and tenderness
  • Fatigue
  • Trouble swallowing or breathing

During a flare up, symptoms of weakness and fatigue can intensify and be accompanied by weight loss, joint inflammation, and fever.[4]

Myositis can also affect other organs, such as the lungs, heart, and digestive system. This can lead to respiratory, cardiac, and digestive symptoms, including chest pain, bloating, indigestion, and constipation.

Dermatomyositis symptoms are identical to symptoms of polymyositis, with the addition of skin rashes and changes (dermal involvement). The rashes tend to be purple-red in color and often appear on the eyelids, face, chest, neck, back, and joints. They are often sensitive to sunlight, bright light, and UV radiation. Those with dermatomyositis may also have calcium deposits under the skin and nail abnormalities.

In inclusion body myositis, the symptoms are more pronounced in the hands and feet, away from the torso. These patients may be more prone to dropping light objects, have difficulty maintaining a grip, or maybe more prone to tripping or stumbling.

The symptoms of myositis may vary depending on the type and severity of the disease. While some people may experience minor symptoms that have little impact on their quality of life, others may experience more serious symptoms that warrant medical treatment.

Risks and Complications

Myositis can also affect the muscles that control breathing, swallowing and the heartbeat. In severe cases, this can lead to devastating consequences, especially in patients with advanced disease.

Possible complications of myositis include:

  • Dysphagia: Difficulty swallowing due to weakness or inflammation of the esophageal muscles. It can lead to choking or indigestion.
  • Pulmonary Aspiration: Food or liquids can enter the lungs when swallowing due to weakened throat muscles. It can cause irritation and lead to pneumonia.
  • Hypoventilation: This occurs when breathing becomes shallow or slow due to weakness of the respiratory muscles. It may result in the body accumulating carbon dioxide or having low oxygen levels in the blood.
  • Interstitial Lung Disease: This is a group of lung conditions that result in lung tissue inflammation or scarring. It may result in chest pain, coughing, or shortness of breath.
  • Heart Arrhythmias: The heart can be impacted by myositis, which can lead to an irregular pulse and an elevated risk of heart conditions such as coronary artery disease.[5]
  • Autoimmune Diseases: Myositis raises the possibility of getting lupus, rheumatoid arthritis, scleroderma, or Sjogren's syndrome, which are all autoimmune conditions.

Triggers and Causes of Myositis

The exact causes of myositis are not well understood. Like most autoimmune diseases, it is believed to be the result of autoimmune genes that increase susceptibility coupled with multiple inflammatory events that cause the immune system to become dysfunctional over time. Some patients may develop myositis as a condition secondary to another systemic autoimmune disease, such as arthritis.

People with myositis may notice their symptoms worsen in response to factors that promote inflammation, known as triggers. Triggers are likely to differ from person to person, yet some of the most common ones include infections, allergies, and injuries. In rare cases, certain medications, such as statins, penicillamine, interferon-alpha blockers, and TNF inhibitors, can cause muscle toxicity and inflammation that triggers myositis.[6]

Myositis Diagnosis

Myositis can be challenging to diagnose because it is a rare condition and has overlapping symptoms with other diseases. To confirm the diagnosis and rule out other potential reasons, the doctor will need to run a number of tests.[7]

Blood tests are the first tests the patient will receive after undergoing a physical examination and sharing their medical history. These tests measure the levels of muscle enzymes, antibodies, and other blood markers of inflammation that indicate muscle damage or inflammation.

The most common blood tests for chronic inflammation used to diagnose myositis include those assessing creatine kinase, C-reactive protein, lactate dehydrogenase, and liver markers.

Creatine Kinase (CK) is an enzyme that seeps into the blood from injured muscle cells.Elevated CK levels suggest muscle breakdown and are commonly used to aid in confirming diagnosis.[8]

Antibodies are also routinely tested in blood tests for myositis. Those including anti-Jo1, anti-PM SCL, anti-Ro, anti-La, anti-Ku, and anti-U1 RNP are frequently associated with all types. Anti-Mi2, anti-MDA5, anti-TIF, anti-SAE, and anti-NXP are unique to dermatomyositis.

If any of these findings are present, the doctor will investigate the muscles more deeply to rule out causes of muscle inflammation, damage, and breakdown.

Other tests required to confirm a myositis diagnosis include:

  • Muscle biopsy, which examines a small muscle sample for abnormalities.
  • Skin biopsy is used to check a skin sample for abnormalities in those with a rash and diagnose dermatomyositis.
  • Electromyography (EMG) to test muscle electrical activity and function.
  • Imaging tests, such as X-rays, ultrasound, MRI, or CT scans, to rule out other possibilities or check for complications.

All these tests give further insight into inflammation levels, muscle or nerve damage, and other changes such as calcification or the presence of a tumor.

Treatment Options

Myositis cannot be cured, however, treatment can lessen symptoms, avert complications, and enhance a patient's quality of life. 

It is important to consult with your healthcare provider to receive an accurate diagnosis and tailored treatment plan. The treatment plan may vary depending on the type and severity of the disease, as well as the individual’s response and tolerance to the medications.

Some of the treatment options for myositis include:[9]

  • Medications: These drugs aim to suppress the immune system and reduce inflammation. They include corticosteroids such as prednisone, immunosuppressants such as methotrexate or azathioprine, biologics such as rituximab or tocilizumab, and immunoglobulin therapy. These medications need to be regularly monitored by the doctor because some of them could have major adverse effects, such as an increased risk of infection, bone loss, diabetes, or liver damage.
  • Therapy: Physical therapy, occupational therapy, and speech therapy can help maintain muscle strength and flexibility, slow muscle atrophy, and improve function and mobility. They can also teach exercises, stretches, and techniques to cope with the symptoms and prevent falls or injuries. To support the afflicted muscles, assistive equipment like braces, splints, or walkers may be required in some cases.
  • Lifestyle changes: These adjustments can help manage the symptoms and enhance general health and well-being. They include eating a balanced diet rich in omega-3 fatty acids[10] and antioxidants, drinking plenty of water, getting enough rest and sleep, avoiding stress and smoking. Some people may wish to keep a diary to help pinpoint triggers of muscle weakness. The benefits of complementary therapies for reducing stress and inflammation include acupuncture, massage, and yoga.[11]

Myositis Prognosis

The prognosis of myositis depends on a number of factors, such as the intensity and nature of the disease, the patient's reaction to treatment, and the occurrence of any complications. For some, the disease can be debilitating and affect daily activities. Remission is documented in a few cases, although symptoms tend to return at a later date.

The key to managing myositis is to seek early diagnosis and treatment, follow the doctor’s recommendations, and adopt a healthy lifestyle.


Myositis is a rare muscle disease that causes inflammation and weakness of the muscles. It can affect different parts of the body and cause various symptoms and complications. There are different types of myositis, each with unique symptom presentations. The prognosis of myositis depends on many factors such as the type and severity of the disease, the response to treatment, and the presence of any complications. Myositis can be a challenging condition to live with, but with proper care and support, it is possible to improve the quality of life.

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