Inclusion Body Myositis (Inflammatory Myopathy)

What is Inclusion Body Myositis?

Inclusion body myositis (IBM) is an inflammatory muscle disease characterised by progressive muscle weakness and wasting. The disorder is similar to another inflammatory myopathy called polymyositis. IBM is often the diagnosis for cases of polymyositis that are unresponsive to therapy, but IBM has its own distinctive features. The onset of muscle weakness in IBM is generally gradual (over months or years). Falling and tripping are usually the first noticeable symptoms. For some patients the disorder begins with weakness in the hands causing difficulty with gripping, pinching, and buttoning. IBM occurs more frequently in men than in women and affects both the proximal (closest to the center of the body) and distal (farthest from the center of the body) muscles. There may be weakness of the wrist and finger muscles and atrophy of the quadricep muscles in the legs. Atrophy or shrinking of the forearms is also characteristic. Difficulty swallowing (dysphagia) occurs in approximately half of IBM cases. Symptoms of the disease usually begin after the age of 50, although the disease can occur earlier.

Is there any treatment?

There is no standard course of treatment for IBM. The disease is unresponsive to corticosteroids and immunosuppressive drugs. Some evidence suggests that intravenous immunoglobulin may have a slight, but short-lasting, beneficial effect in a small number of cases. Physical therapy may be helpful in maintaining mobility. Other therapy is symptomatic and supportive.

What is the prognosis?

IBM is generally resistant to all therapies, and its rate of progression appears to be unaffected by any currently available treatments.