Inflammatory myopathy

Overview

Inflammatory myopathy refers to a group of diseases characterized by inflammation of the muscles, leading to muscle weakness and damage. These conditions are classified as autoimmune diseases, where the body's immune system mistakenly attacks its own muscle tissue. The most common types of inflammatory myopathies include dermatomyositis, polymyositis, and inclusion body myositis.

Types of Inflammatory Myopathy

Dermatomyositis

Characteristic rash of dermatomyositis

Dermatomyositis is an inflammatory myopathy that affects both the skin and muscles. It is characterized by a distinctive rash, often appearing as a heliotrope rash on the eyelids or a rash on the knuckles known as Gottron's papules. Muscle weakness typically affects the proximal muscles, such as those in the hips, thighs, shoulders, and neck.

Polymyositis

Polymyositis is another form of inflammatory myopathy that primarily affects the skeletal muscles. Unlike dermatomyositis, polymyositis does not involve a skin rash. It is more common in adults and is characterized by symmetrical muscle weakness, particularly in the proximal muscles.

Inclusion Body Myositis

Inclusion body myositis (IBM) is a progressive muscle disorder that is more common in older adults. It is characterized by muscle weakness and wasting, particularly in the quadriceps and forearm muscles. Unlike other inflammatory myopathies, IBM often presents with both proximal and distal muscle weakness.

Symptoms

The symptoms of inflammatory myopathy can vary depending on the specific type, but common symptoms include:

• Muscle weakness
• Fatigue
• Difficulty swallowing (dysphagia)
• Muscle pain and tenderness
• Skin rashes (in dermatomyositis)

Diagnosis

The diagnosis of inflammatory myopathy typically involves a combination of clinical evaluation, laboratory tests, and imaging studies. Common diagnostic tools include:

• Blood tests to measure levels of muscle enzymes such as creatine kinase (CK)
• Electromyography (EMG) to assess electrical activity in muscles
• Muscle biopsy to examine muscle tissue for signs of inflammation
• Magnetic resonance imaging (MRI) to visualize muscle inflammation

Treatment

Treatment for inflammatory myopathy often involves the use of immunosuppressive drugs to reduce inflammation and suppress the immune system. Common medications include:

• Corticosteroids such as prednisone
• Immunosuppressants like methotrexate or azathioprine
• Intravenous immunoglobulin (IVIG) therapy

Physical therapy and exercise are also important components of treatment to maintain muscle strength and function.

Prognosis

The prognosis for individuals with inflammatory myopathy varies depending on the type and severity of the disease. With appropriate treatment, many patients experience significant improvement in symptoms. However, some forms, such as inclusion body myositis, may have a more chronic and progressive course.

Related Pages

• Autoimmune disease
• Muscle biopsy
• Corticosteroid
• Immunosuppressive drug