Sporadic Inclusion Body Myositis

FAQ – Frequently Asked Questions

What does the name “inclusion body myositis” mean?

Inclusion body myositis (IBM) is a disease characterized by:

  • Small abnormal particles called “inclusion bodies” that can be seen inside muscle cells when they are viewed with a microscope
  • Muscle inflammation (myo = muscle, -itis = inflammation)

Why is it sometimes called “sporadic” inclusion body myositis (sIBM)?

Inclusion body myositis is sometimes called sporadic inclusion body myositis, or sIBM, to indicate that it is not inherited, but rather seems to occur at random. In general, inclusion body myositis does not run in families. There are extremely rare cases of two siblings in the same family having inclusion body myositis; this has been called familial inclusion body myositis. Also, recent research has shown that a few sporadic inclusion body myositis patients have mutations in genes known to be involved in muscle diseases. However, these situations are unusual, and gene mutations have not been found in most sIBM patients.

How do you pronounce myositis?


Does inclusion body myositis affect lifespan?

Most people who have inclusion body myositis die from other causes. People with IBM sometimes die early because of aspiration pneumonia, caused when food or liquid enters the lungs, which can occur in IBM because of swallowing problems. Occasionally someone with IBM will die because of an IBM-related fall. It used to be said that people with IBM have a normal lifespan, but recent studies seem to indicate that average lifespan is shortened by about three years.

How common is inclusion body myositis?

IBM is a rare disease, and the exact prevalence of the disease is unknown. Medical studies have provided varying answers. The occurrence of the disease may not be the same in all geographic areas and ethnic groups. Also, IBM is often undiagnosed or misdiagnosed, so surveys may not discover all of the actual cases. A common estimate is that about 25,000 people in the United States have inclusion body myositis.

Is inclusion body myositis contagious?

Does inclusion body myositis affect men and women equally?

IBM is somewhat more common in men.

Is there any treatment for inclusion body myositis?

There is no effective drug treatment for most people with inclusion body myositis. Exercise and physical therapy can be useful to help maintain physical function for as long as possible. Many things can be done to manage the disease and improve the lives of people with IBM.

Is hereditary inclusion body myopathy (hIBM) an inherited version of inclusion body myositis?

No, they are entirely different diseases.  Hereditary inclusion body myopathy, or hIBM, actually refers to a group of several separate, very rare genetic disorders. Like inclusion body myositis, these disorders do cause muscle weakness, and the muscle tissue does have inclusion bodies when examined with a microscope. However, these hereditary myopathies usually starts in young adulthood, have different patterns of muscle weakness than inclusion body myositis, and usually do not cause muscle inflammation (that is why the word “myopathy” is used rather than “myositis” — “myopathy” simply indicates muscle disease, while “myositis” refers to muscle inflammation).

The term hereditary inclusion body myopathy is becoming less common, as individual disorders are being named by referring to their associated genetic defect. For example, hereditary inclusion body myopathy type 2 is now known as GNE myopathy, since it is caused by a mutation in the GNE gene.

by Kevin Dooley, MD

Revised July 7, 2023

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