Inclusion body myositis

Inclusion body myositis (IBM) is a progressive muscle disorder characterized by muscle inflammation, weakness, and atrophy (wasting). It is a type of inflammatory myopathy. IBM develops in adulthood, usually after age 50. The symptoms and rate of progression vary from person to person. The most common symptoms include progressive weakness of the legs, arms, fingers, and wrists. Some people also have weakness of the facial muscles (especially muscles controlling eye closure), or difficulty swallowing (dysphagia). Muscle cramping and pain are uncommon, but have been reported in some people.

Most people with IBM progress to disability over a period of years. In general, the older a person is when IBM begins, the more rapid the progression of the condition. Most people need assistance with basic daily activities within 15 years, and some people will need to use a wheelchair. Lifespan is thought to be normal, but severe complications (e.g. aspiration pneumonia) can lead to loss of life.

The underlying cause of IBM is poorly understood and likely involves the interaction of genetic, immune-related, and environmental factors. Some people may have a genetic predisposition to developing IBM, but the condition itself typically is not inherited.

There is currently no cure for IBM. The primary goal of management is to optimize muscle strength and function. Management may include exercise, fall prevention, physical therapy, occupational therapy, and speech therapy (for dysphagia). There is limited evidence that a small proportion of patients may benefit from drugs that suppress the immune system (particularly those with underlying autoimmune disorders), but this therapy is otherwise typically not recommended.