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What is Myositis?

Myositis is a group of rare autoimmune diseases in Singapore that primarily affect the muscles and cause inflammation and muscle weakness. The term "myositis" is derived from the Greek words "myo," which means muscle, and "itis," which means inflammation. There are several different types of myositis, but the most common ones include:

  • Polymyositis: polymyositis primarily affects the skeletal muscles, causing muscle weakness, pain, and fatigue. It often leads to difficulties with mobility and muscle strength.
  • Dermatomyositis: dermatomyositis is similar to polymyositis but involves skin changes. Patients with dermatomyositis typically develop a characteristic rash on the skin, which may occur on the face, knuckles, elbows, knees, and other body parts.
  • Inclusion body myositis: inclusion body myositis is a slowly progressing muscle disease typically affecting older individuals. It is characterised by muscle weakness and atrophy, especially in the muscles of the hands and fingers.
Muscle pain myositis
Myositis is characterised by strained and inflamed muscles.

What causes Myositis?

The exact cause of myositis is not fully understood, but it is believed to be related to an autoimmune response. Autoimmune diseases occur when the body's immune system, designed to protect against infections and foreign substances, mistakenly attacks its healthy tissues and organs. In the case of myositis, the immune system targets muscle tissue, leading to inflammation, muscle damage, and weakness.

What are the symptoms of Myositis?

Myositis is characterised by muscle inflammation, and its symptoms vary depending on the specific type of myositis and the individual affected. The primary symptom of myositis is muscle weakness, but other symptoms may also be present. Here are common symptoms associated with myositis:

  • Muscle weakness: muscle weakness is a hallmark symptom of myositis. It typically begins in the muscles closest to the body's trunk and can progress over time. The weakness can affect mobility, including standing, climbing stairs, lifting objects, or performing daily activities.
  • Muscle pain: individuals with myositis often experience muscle pain or discomfort, which ranges from mild to severe and may be associated with muscle inflammation.
  • Fatigue: muscle weakness and inflammation can lead to fatigue, which can be both physical and mental. People with myositis may feel exhausted and lacking in energy.
  • Skin changes (dermatomyositis): individuals with dermatomyositis may develop characteristic skin changes, including a rash on the face, knuckles, elbows, knees, and other areas. The skin rash can be reddish or purplish.
  • Difficulty swallowing: some types of myositis, such as inclusion body myositis, can lead to difficulties in swallowing – dysphagia.
  • Joint pain: joint pain and inflammation can occur in addition to muscle symptoms in some cases, particularly in overlap syndromes where myositis is associated with other autoimmune diseases.
  • Muscle atrophy: sometimes, persistent muscle weakness and inflammation can lead to muscle atrophy, where the affected muscles become smaller and weaker.
  • Breathing problems: in severe cases, myositis can affect the muscles involved in breathing, leading to respiratory issues and shortness of breath.
  • Swelling and tenderness: affected muscles may become swollen and tender to the touch due to inflammation.

It is important to note that myositis symptoms vary from person to person, and the specific symptoms depend on the type of myositis and the severity of the disease.

If you suspect you have myositis or are experiencing any of the symptoms mentioned above, make an appointment with Asia Arthritis Rheumatology Clinic today.

Is Myositis painful?

Yes, myositis can be painful, and muscle pain is a common symptom associated with this condition. The pain in myositis is typically due to inflammation and damage to the muscle tissue. Inflammation of the muscles can lead to localised pain, tenderness, and discomfort. The severity of pain varies from person to person and may range from mild to severe.

Muscle pain from myositis can be aggravated by movement or activity. The pain is often described as aching, cramping, or a deep, persistent discomfort. In addition to muscle pain, some types of myositis, such as dermatomyositis, may also cause skin-related symptoms like a rash, which can be itchy or painful.

Who is at risk of Myositis in Singapore?

Myositis is a relatively rare group of autoimmune diseases, and while it can affect anyone, certain factors may increase the risk of developing myositis. These risk factors include:

  • Age: dermatomyositis can occur in two groups of individuals – in children between the ages of 5 and 15 and adults between the ages of 40 and early 60s. Polymyositis typically occurs between the ages of 30 and 60, while inclusion body myositis is more common in individuals above 50.
  • Gender: myositis can affect males and females, but certain subtypes may have a slightly higher prevalence in one gender. For instance, polymyositis and dermatomyositis are more common in females, while inclusion body myositis affects males more frequently.
  • Genetics: some individuals with a family history of autoimmune diseases or myositis may have a higher risk of developing the condition. Specific genetic factors associated with myositis are still under investigation.
  • Autoimmune conditions: people with other autoimmune diseases, such as systemic lupus erythematosus, rheumatoid arthritis, or Sjögren's syndrome, may be at a higher risk of developing myositis. This is known as an overlap syndrome, where an individual has multiple autoimmune conditions.
  • Environmental factors: certain environmental factors, such as infections or exposure to toxins, may trigger myositis in individuals with a genetic predisposition. Sometimes, an infection can activate the immune response and lead to infective myositis.

While these factors may be associated with an increased risk of myositis, not everyone with these risk factors will develop the condition. Myositis remains a relatively rare disease; most cases do not have a clear, identifiable cause.

How is Myositis diagnosed?

The specific tests and diagnostic approach vary depending on the type and presentation of myositis, but in general, diagnosing myositis involves the following:

  • Medical history and physical examination: a detailed medical history, including a discussion of your symptoms, their onset, and their progression will be obtained. A physical exam will assess muscle strength, tenderness, and any visible skin changes (in cases of dermatomyositis).
  • Blood tests: blood tests to diagnose myositis include:
    • Creatine kinase (CK) level: elevated CK levels in the blood can be a marker of muscle damage.
    • Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels: these tests can indicate the presence of inflammation.
    • Antinuclear antibodies (ANA): the presence of specific autoantibodies can help identify autoimmune processes.
    • Myositis-specific and myositis-associated autoantibodies: these autoantibodies are often found in people with myositis and can provide valuable diagnostic information.
  • Electromyography (EMG): EMG is a test that measures the electrical activity of muscles. Abnormal patterns in the electrical activity can help identify muscle damage and weakness.
  • Muscle biopsy: a muscle biopsy involves the removal of a small piece of muscle tissue for examination under a microscope. This procedure can confirm the presence of muscle inflammation and help determine the specific type of myositis.
  • Imaging studies: magnetic resonance imaging (MRI) or ultrasound can be used to assess muscle inflammation and damage. These imaging studies provide additional information about the extent of muscle involvement.
  • Skin biopsy (dermatomyositis): in cases of dermatomyositis, a skin biopsy may be performed to examine skin changes, such as the characteristic skin rash.
  • Additional tests: additional tests may be necessary to rule out other conditions that can mimic myositis, such as other autoimmune diseases or metabolic disorders.
EMG muscles
Electromyography measures the electrical activity of muscles.

What are the treatment options for Myositis in Singapore?

Treatment for myositis is aimed at reducing inflammation, managing symptoms, and improving muscle strength and function. The specific treatment approach may vary depending on the type and severity of myositis. Common treatment options for myositis include:

  • Immunosuppressive medications: immunosuppressive medications are often the mainstay of myositis treatment. They work to suppress the immune system's overactivity, reduce inflammation, and slow down the progression of the disease. Common immunosuppressive medications include:
    • Glucocorticoids (such as prednisone): these are often used initially to control inflammation but are usually tapered to the lowest effective dose to minimise side effects.
    • Immunosuppressive drugs: may be combined with glucocorticoids or as alternatives to help reduce the immune response.
  • Intravenous immunoglobulin (IVIg): intravenous immunoglobulin, a solution of human antibodies, may be used in some individuals to help modulate the immune system and manage myositis symptoms.
  • Biologic therapies: certain biologic medications, such as rituximab, are used in refractory cases of myositis or when other treatments are ineffective. These drugs target specific components of the immune system.
  • Physical and occupational therapy: physical and occupational therapy can help improve joint mobility, strengthen muscles, reduce pain, and help individuals with myositis learn strategies to manage daily tasks. Occupational therapists can also provide strategies and assistive devices to enhance independence.
  • Diet and nutrition: maintaining a balanced and nutritious diet supports overall health and well-being. It can help address any weight loss or nutritional deficiencies associated with myositis.
intravenous immunoglobulin
Intravenous immunoglobulin infusion may be used to treat symptoms related to myositis.

In some cases, individuals with myositis may experience periods of disease remission, where symptoms are less severe or absent. However, myositis is typically a chronic condition that requires ongoing management and care. The goal of treatment is to achieve the best possible quality of life by controlling inflammation, minimizing muscle weakness, and managing associated symptoms.

Make an appointment with Asia Arthritis Rheumatology Centre where we prioritise our patient’s health by ensuring accurate diagnosis and personalised treatment.

Frequently Asked Questions

Is myositis a curable condition?

Myositis is a chronic condition with no known cure. However, early diagnosis and appropriate treatment can help manage symptoms, reduce inflammation, and improve the quality of life for individuals with myositis.

Is myositis a type of muscular dystrophy?

No, myositis is not a form of muscular dystrophy. Muscular dystrophy is a group of genetic disorders, while myositis is primarily an autoimmune disease affecting the muscles.

Can myositis go into remission, and what does that mean for individuals with the condition?

Myositis can sometimes go into remission, where symptoms become less severe or even disappear. Achieving remission may involve the right combination of medications and treatment. However, it is essential to continue monitoring and follow medical advice during remission.

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Dr Annie Law

Senior Consultant Rheumatologist
FAMS (Rheumatology)

Dr Annie Law is an experienced Senior Consultant Rheumatologist and Medical Director at Asia Arthritis & Rheumatology Centre.

She leads subspecialty SLE clinics, showcasing her dedication to lupus care. Dr Annie Law has been duly recognised for patient-oriented care, earning multiple awards. Her extensive education includes FAMS (Rheumatology) and MRCP (General Medicine). Actively involved in lupus research, she established a lupus database and contributed to paramount protein therapy discoveries. Dr Law is a committed medical educator, holding faculty positions and receiving accolades for her teaching. Her impactful contributions extend to the professional organisation for rheumatology in Singapore exemplifying deep commitment to advancing rheumatology knowledge.

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