Myositis is a group of rare autoimmune diseases characterised by inflammation and degeneration of muscle tissue. This condition leads to muscle weakness, pain, and fatigue, impacting the ability to perform daily activities. Myositis can affect individuals of all ages but is more common in adults. Early diagnosis and treatment are essential to managing symptoms and preventing complications.

Types of Myositis

There are several types of myositis, each with distinct features and associated symptoms. The most common types include:

Polymyositis

  • Characteristics – Inflammation and weakness of muscles, primarily affecting those closest to the trunk of the body (e.g., shoulders, hips, thighs, neck). Symmetrical muscle involvement means both sides of the body are affected equally.
  • Age of Onset – Typically occurs in adults between 30 and 60 years old.
  • Symptoms – Gradual onset of muscle weakness, difficulty climbing stairs, lifting objects, or rising from a seated position.

Dermatomyositis

  • Characteristics – Similar muscle inflammation and weakness as polymyositis, but with a distinctive skin rash. A rash may appear as a violet-coloured or dusky red rash, typically on the face, eyelids, knuckles, elbows, knees, chest, and back.
  • Age of Onset – This can occur at any age but has peaks in children (juvenile dermatomyositis) and adults.
  • Symptoms – Muscle weakness, rash, difficulty swallowing, and respiratory issues if chest muscles are affected.

Inclusion Body Myositis (IBM)

  • Characteristics – Slow, progressive muscle weakness and wasting, often asymmetrical. Affects both proximal and distal muscles, including those of the fingers and wrists.
  • Age of Onset – Typically affects individuals over the age of 50.
  • Symptoms – Muscle weakness, frequent falls, difficulty gripping objects, and sometimes mild muscle pain.

Necrotizing Autoimmune Myopathy (NAM)

  • Characteristics – Severe, acute muscle weakness with elevated levels of muscle enzymes.
  • Muscle biopsy shows necrosis (death) of muscle fibers without significant inflammation.
  • Age of Onset – Can occur at any age but more common in adults.
  • Symptoms – Rapid onset of severe muscle weakness, often requiring aggressive treatment.

Symptoms of Myositis

Symptoms of myositis vary depending on the type and severity of the disease. Common symptoms include:

Muscle-Related Symptoms

  • Weakness – Progressive muscle weakness, especially in proximal muscles (e.g., hips, shoulders).
  • Pain – Muscle pain and tenderness.
  • Fatigue – General tiredness and lack of energy.

Systemic Symptoms

  • Skin Rash – Distinctive rashes, especially in dermatomyositis.
  • Difficulty Swallowing – Dysphagia is due to the involvement of oesophagal muscles.
  • Breathing Problems – Respiratory muscle involvement leading to shortness of breath.
  • Joint Pain – Arthralgia or arthritis in some cases.
  • Fever – Low-grade fever in active phases.

Causes of Myositis

The exact cause of myositis is unknown, but it is believed to involve a combination of genetic, environmental, and immune factors.

Genetic Factors

  • Family History – Increased risk in individuals with a family history of autoimmune diseases.
  • Genetic Predisposition – Certain genetic markers may increase susceptibility to myositis.

Environmental Triggers

  • Infections – Viral, bacterial, or parasitic infections may trigger the onset of myositis in genetically predisposed individuals.
  • Medications – Some drugs, such as statins, can induce myositis-like symptoms.
  • Environmental Exposures – Exposure to certain chemicals or toxins.

Immune System Dysfunction

  • Autoimmunity – The immune system mistakenly attacks muscle tissue, leading to inflammation and damage.

Diagnosis of Myositis

Diagnosing myositis involves a combination of clinical evaluation, laboratory tests, and imaging studies.

Clinical Evaluation

  • Symptom Review – Detailed discussion of symptoms, including their duration, severity, and pattern.
  • Medical History – Review of personal and family medical history, including any autoimmune diseases.
  • Physical Examination – Comprehensive examination to assess muscle strength, skin changes, and joint involvement.

Diagnostic Tests

  • Blood Tests – Elevated levels of muscle enzymes (e.g., creatine kinase, aldolase).Presence of specific autoantibodies (e.g., anti-Jo-1, anti-Mi-2).
  • Electromyography (EMG) – To assess the electrical activity of muscles and detect abnormalities.
  • Muscle Biopsy – Examination of muscle tissue to confirm inflammation, necrosis, or inclusion bodies.
  • Imaging Studies – MRI to visualise muscle inflammation and damage.

Myositis Treatment

The treatment of myositis aims to control inflammation, improve muscle strength, and prevent complications. A multidisciplinary approach involving rheumatologists, neurologists, dermatologists, and other specialists is often required.

Medications

  • Corticosteroids – These medications reduce inflammation and suppress the immune system.
  • Immunosuppressive Drugs – These medications are used to suppress the immune response in severe cases.
  • Biologic Agents – These agents are used for patients with refractory myositis.
  • Antimalarial Drugs – These medications are used to treat skin symptoms in dermatomyositis.

Physical Therapy and Rehabilitation

  • Exercise Programs – Tailored physical therapy to improve muscle strength, flexibility, and range of motion.
  • Occupational Therapy – Assistance with adapting daily activities to minimise muscle strain and improve function.

Lifestyle Modifications

  • Healthy Diet – Consuming a balanced diet supports overall health and manages medication side effects.
  • Regular Exercise – Engaging in low-impact activities like swimming, cycling, and walking to maintain muscle strength and joint flexibility.
  • Rest and Stress Management – Getting adequate rest and managing stress through relaxation techniques, counselling, or support groups.

Living with Myositis

Managing myositis involves ongoing care, lifestyle adjustments, and support to maintain quality of life.

Self-Care Strategies

  • Adherence to Treatment – Following prescribed medication regimens and attending all medical appointments.
  • Healthy Diet – Consuming a balanced diet supports overall health and reduces inflammation.
  • Regular Exercise – Engaging in physical activity as tolerated to maintain muscle strength and joint flexibility.
Myositis is a complex and potentially debilitating condition, but with effective management strategies, individuals with myositis can lead active and fulfilling lives. Early diagnosis, appropriate treatment, and a supportive environment are key to improving outcomes and maintaining quality of life for those affected by myositis.

Got Questions? Consult a trusted Rheumatology specialist today.