Myositis is a group of rare inflammatory conditions characterized by muscle inflammation and weakness. It can affect various muscle groups and, in some cases, other parts of the body such as the skin, lungs, or joints. The severity of myositis can range from mild muscle weakness to severe, disabling symptoms.
Types of Myositis
- Polymyositis:
- Affects multiple muscles, primarily those near the trunk (shoulders, hips).
- More common in adults, especially middle-aged individuals.
- Dermatomyositis:
- Includes muscle inflammation and a distinctive skin rash.
- Can affect both adults and children (juvenile dermatomyositis in children).
- Inclusion Body Myositis (IBM):
- Gradual onset of muscle weakness, primarily in older adults.
- Affects both proximal and distal muscles (e.g., thighs, forearms, and hands).
- Necrotizing Autoimmune Myopathy:
- Severe muscle weakness caused by rapid muscle cell destruction.
- Often linked to autoimmune reactions or medication (e.g., statins).
- Infectious Myositis:
- Caused by infections, such as viral (e.g., influenza, HIV), bacterial, or parasitic infections.
- Idiopathic Inflammatory Myositis:
- Includes cases where the cause of inflammation is unknown.
Symptoms
- Muscle Weakness:
- Difficulty climbing stairs, lifting objects, or rising from a seated position.
- Progressive in nature, often affecting both sides of the body.
- Fatigue.
- Muscle Pain or Tenderness.
- Skin Changes (in Dermatomyositis):
- Red or purple rash on the face, eyelids, knuckles, knees, or elbows.
- Difficulty Swallowing (Dysphagia).
- Shortness of Breath:
- Due to lung involvement in some cases (interstitial lung disease).
- Joint Pain or Stiffness.
- Fever (in infectious myositis).
Causes
The exact cause of myositis is not always clear but can include:
- Autoimmune Conditions:
- The immune system mistakenly attacks healthy muscle tissue.
- Infections:
- Viral, bacterial, or parasitic infections can trigger muscle inflammation.
- Medications:
- Certain drugs, such as statins or biologics, may induce myositis.
- Genetics:
- Some forms may have a genetic component.
Risk Factors
- Gender: Some types (e.g., polymyositis, dermatomyositis) are more common in women.
- Age: Certain types are more prevalent in children or older adults.
- Family History: A family history of autoimmune disorders may increase the risk.
Diagnosis
Diagnosing myositis involves a combination of medical history, physical examination, and diagnostic tests:
- Blood Tests:
- Elevated levels of muscle enzymes (e.g., creatine kinase).
- Autoantibodies indicating autoimmune activity.
- Electromyography (EMG):
- Measures electrical activity in muscles.
- Muscle Biopsy:
- Examines muscle tissue for inflammation or damage.
- Imaging:
- MRI to detect inflammation in muscles.
- Pulmonary Function Tests:
- To evaluate lung involvement in certain cases.
Treatment
- Medications:
- Corticosteroids (e.g., prednisone): Reduce inflammation.
- Immunosuppressants (e.g., methotrexate, azathioprine): Help manage autoimmune activity.
- Biologic Therapies (e.g., rituximab): Target specific immune system components.
- Physical Therapy:
- Maintains muscle strength and improves mobility.
- Diet and Nutrition:
- Balanced nutrition supports overall health and energy levels.
- Infection Management (for infectious myositis):
- Antiviral, antibacterial, or antiparasitic medications.
- IV Immunoglobulin (IVIG):
- Used in severe cases to modulate the immune response.
Complications
- Progressive muscle weakness affecting daily activities.
- Breathing difficulties if respiratory muscles are involved.
- Swallowing difficulties, increasing the risk of choking or aspiration pneumonia.
- Lung damage in cases with interstitial lung disease.
Prognosis
The outlook depends on the type and severity of myositis:
- Polymyositis and Dermatomyositis: Often improve with treatment, but relapses can occur.
- Inclusion Body Myositis (IBM): Progresses slowly and is more challenging to treat.
- Infectious Myositis: Typically resolves with appropriate treatment.Early diagnosis and comprehensive treatment are key to managing symptoms and preventing complications.
