Sporadic Inclusion Body Myositis—Frequently Asked Questions (FAQ)

Why is IBM called “inclusion body myositis”?

“Inclusion body” is part of the name because of small, abnormal particles called “inclusion bodies” that can be seen inside IBM muscle cells when they are viewed with a microscope. “Myositis” is a term that refers to a group of diseases characterized by muscle inflammation (myo = muscle, -itis = inflammation).

Why is IBM 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?

My-oh-SIGH-tis

Do people die from inclusion body myositis?

It used to be said that inclusion body myositis does not cause death or affect lifespan, but recent studies indicate that average lifespan is shortened by a few years. Most people with IBM die from causes unrelated to IBM. The most common causes of death are aspiration pneumonia, caused when food or liquid enters the lungs, and respiratory failure.

How common is inclusion body myositis?

A common estimate is that about 25,000 people in the United States have inclusion body myositis. Many studies show a prevalence in people 50 and older of between 25 and 150 per million. Differences in estimates may be due to a high number of undiagnosed cases and also to geographic differences.

Is inclusion body myositis contagious?

No, IBM is not contagious. Someone with IBM cannot give it to another person.

Does inclusion body myositis affect men and women equally?

IBM is more common in men, in a ratio of approximately 2:1 to 3:1.

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 May 1, 2024

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