How is it diagnosed?

To diagnose myositis, your doctor will ask you a series of questions about your symptoms, perform a physical exam and order several laboratory tests. Some patients will be admitted to the hospital for some of the tests and for observation. If your weakness is progressive and you are unable to care for yourself or if your breathing muscles are involved, you will likely be admitted to the hospital.

Some of the tests your doctor will perform include the following:

• Physical Exam
• Muscle strength and tenderness assessment
• Observation joint swelling, pain or tenderness
• Evidence of skin disease will be sought
• Examination of the nail beds for telangiectasias, which are small red marks caused by dilated blood vessels.
  
• Laboratory Tests
  
  
  • Creatine kinase (CK): A blood test to assess levels of creatine kinase will be ordered. CK is an enzyme found mainly in muscles. When muscles are damaged, it leaks out into the bloodstream, causing CK levels in the blood to rise. CK levels tend to go up with increasing disease activity and go down as the disease improves.
  • Erythrocyte sedimentation rate (ESR): The ESR (also known as sed rate) is normal in 50 percent of patients with myositis and is elevated above 50 mm/hour in only 20 percent.
    
    
    
  • Other blood tests: A few other blood and laboratory tests may be performed to exclude other conditions, such as lupus, rheumatoid arthritis and scleroderma.
  • Electromyogram (EMG): An EMG will be order to measure the electrical activity of muscle. An EMG involves the insertion of needle-like electrodes into muscles to stimulate and record their activity. The test can distinguish between muscle weakness caused by nerve damage and that caused by muscle fiber damage. The test may be uncomfortable.
  • Muscle biopsy: A biopsy of an affected muscle is used to confirm the diagnosis. This may require a surgical incision under a local anesthetic. Muscle biopsy shows whether and how the muscle fibers are damaged. It also helps determine what type of myositis you have.
  • Autoantibodies: Several autoantibodies are found almost exclusively in people with myopathies. Although myositis-specific autoantibodies (MSA) are found in fewer than 50 percent of patients, the presence of a particular MSA identifies a group of patients that share clinical features and prognosis.
  • Cancer screening: Tests may be performed in older patients and men, because myositis in these individuals can be associated with cancer.
  • Magnetic resonance imaging (MRI): An MRI may be done to see evidence of inflammation in the muscles.

Before beginning treatment, your doctor may run certain tests for baseline data for comparison during treatment. The strength of individual muscle groups, muscle enzyme levels, chest X-rays, pulmonary function studies and swallowing studies may be indicated.

Treatment for the myopathies includes the following:

• Rest: During intervals of severe inflammation, periods of increased rest may be necessary. Passive range-of-motion exercises (this is when someone else moves your joints and muscles for you) during these intervals will help prevent your muscles from wasting and your tendons and ligaments from stiffening.
• Physical therapy: Physical therapy plays an important role in treatment to maintain flexibility and reduce risk of muscle atrophy. Range of motion exercises reduce stiffness and keep your joints mobile, strengthening exercises maintain or increase muscle strength, and endurance exercises strengthen your heart and give you energy.
• Corticosteroids: The standard first-line medication for any inflammatory myopathy is corticosteroids. Improvement may be noted in the first weeks or gradually, over three to six months. As many as 90 percent of patients improve at least partially with corticosteroid therapy, and 50 to75 percent of those patients achieve complete remission.