Inclusion Body Myositis

Inclusion Body Myositis (IBM), also call sporadic inclusion body myositis (sIBM), is most prominent in men over the age of 50. IBM affects men slightly more than women, and while most literature states ages 50 and older, our experience shows many cases with patients in their 30’s and 40’s.

IBM is rare inflammatory, degenerative neuromuscular disease in which inflammatory cells invade muscle tissue causing progressive muscle weakness and muscle wasting. IBM is distinct from other inflammatory myopathies in that muscle degeneration occurs. One of the hallmark signs of IBM are small abnormal particles, called inclusion bodies, which are clumps of discarded cellular material that collect in the muscle tissues and are seen on muscle biopsy.

IBM is slow, progressive muscle disease that causes severe weakness and muscle atrophy in the forearms, including the muscles controlling finger movements. IBM typically affects the muscles of the arms and legs, particularly the thigh (quadriceps) muscle and muscles in the lower legs that move the feet. The weakness is not necessarily the same on both sides of the body such as is usual with other forms of inflammatory myopathies. Typically patients with IBM do not experience severe muscle pain, but some report discomfort, aches, and pain.

The first muscles some report to be affected with Inclusion Body Myositis are the wrists and fingers, and the muscles at the front of the thigh. The muscles that lift the front of the foot also may be affected early causing foot drop and frequent falls. (see image to the right).

IBM is a rare disease affecting men more than women. Approximately 5 to 10 people per million in the U.S. are diagnosed with a form of Myositis each year.

Sporadic Inclusion Body Myositis (sIBM)

Sporadic Inclusion Body Myositis is the type we focus on as one of the Idiopathic Inflammatory Myopathies. It is a rare, inflammatory muscle disease with no known cause. It is also considered an Acquired Myopathy, one which is not caused by genetic inheritance.

IBM is the most common inflammatory muscle disease in adults older than 50 and is found in men more often than women. Symptom onset occurs gradually, typically over a period of years, most often after the age of 50. It is not uncommon for people with IBM to require a wheelchair within 10 to 15 years of disease onset.

The cause of inflammatory myopathies like IBM is unclear. For some reason, in the case of sIBM, the body’s immune system turns against itself, referred to as an autoimmune response, and damages muscle tissue. The cause of the progressive muscle degeneration that occurs in IBM is unclear as well.

Life with Inclusion Body Myositis

At this time there are no approved treatments for sIBM. While the disease is slowly progressing, patients will typically require assistive devices within 10-15 after diagnosis, or disease onset. This may evolve from using a cane to a walker and eventually a wheelchair. Some may lose total arm and leg function as well.

Life expectancy is not thought to be affected. The majority of deaths due to IBM are from complications from dysphagia which can lead to aspiration pneumonia.

Living with IBM is about learning to adapt. Many will require home modifications to make life in a wheelchair easier.

Getting support as a patient and for those who are caregivers is important. We offer several support options for IBM patients so they can learn from one another and get ideas on adapting to the disease from those who have been there.

Familial Inclusion Body Myositis

Familial inflammatory inclusion body myositis is an extremely rare condition that has been reported in multiple members of several different families. The symptoms of this fIBM resemble those of sIBM including a later age of onset and a similar pattern of muscle involvement, especially the involvement of the quadriceps muscle and the muscles of the fingers and hands.

Each case/patient with IBM may be quite different from others.  There have been cases where people originally diagnosed with Polymyositis (PM) that were not responding to standard treatments later found they actually have IBM or a non-inflammatory Myopathy such as a form of Muscular Dystrophy.

Inherited Inclusion Body Myopathy (hIBM)

(Not a part of the inflammatory myopathies)

Inherited Inclusion Body Myopathies (hIBM) are a group of rare genetic disorders. hIBM causes progressive muscle wasting and weakness that begins in young adulthood and into the early twenties and thirties, and can lead to very severe disability within 10 – 20 years.This form of the disease is NOT an Acquired Myopathy or an Idiopathic Inflammatory Myopathy as it has a genetic cause. hIBM lacks lymphocyte inflammation (inflammation) therefore it is a “myopathy” rather than “myositis.”

The hereditary inclusion body myopathies may be inherited as autosomal dominant or recessive traits and are caused by mutations of specific genes.

Inclusion body myopathy with early-onset Paget disease and frontotemporal dementia (IBMPFD) is a part of the inherited inclusion body myopathy family.

Tools: Inclusion Body Myositis – Functional Rating Scale (IBM-FRS)

The Functional Rating Scale (IBM-FRS) for Inclusion Body Myositis is used by physicians and researchers. There is also an IBM Patient Functional scale that is more detailed and can help your doctors and hospital staff understand your needs as an inpatient. Download the files below and ask that it be made a part of your medical records.

Diagnosing Inclusion Body Myositis

IBM on presentation can look like Amyotrophic lateral sclerosis (ALS) in that it affects middle-aged and older people and often affects the swallowing muscles early on. However, ALS is a nerve disease, not a muscle disease.

IBM may also appear much like polymyositis at first in that both are inflammatory muscle diseases that involve weakness of the arms and legs. However, many patients with polymyositis, aside from refractory cases, will respond to treatments such as corticosteroids and immunosuppressive medications while IBM patients do not. Part of the misdiagnosis can be muscle biopsy findings. Lack of the inclusion bodies/rimmed vacuoles on biopsy does not necessarily rule out IBM as these may not show on biopsy until later progression of IBM. The symptoms and patient history, along with the all important physical exam must be taken into account.

Important patient and clinical findings related to sIBM may include: 

• History of slowly progressing muscle weakness with frequent falls
• Asymmetric muscle weakness
• Weakness of swallowing muscles (dysphagia)
• Finger flexor and wrist flexor weakness
• Knee extensor weakness usually greater than hip flexor weakness
• Anti-NT5C1A antibodies (helpful in adding a piece to the diagnosis if present)
• EMG that shows large motor unit potentials which can be misinterpreted as a neurogenic process
• MRI findings of muscle edema (swelling), muscle wasting, and fatty infiltration of muscles
• Muscle biopsy showing endomysial inflammation with invasion of non-necrotic muscle fibers, rimmed vacuoles, and atrophic muscle fibers

IBM and Dysphagia

Dysphagia, weakness in the muscles involved in swallowing, is a significant problem as it has been reported to affect 50 to 70% of patients.

Have you been diagnosed with sIBM?

Or, are you a direct caregiver to someone who has been?

We have a support group just for those living with sIBM, sporadic inclusion body myositis, and their direct caregivers.

As part of our commitment to help myositis patients, we have several online support groups. What makes the IBM support group helpful is that often the discussion surrounding IBM, vs. that of PM, DM, NAM, and other forms, is less about treatment options, since none currently exist, and more about learning to cope, adapt, and live with this rare muscle disease.

And, since we know how difficult it can be for anyone with a muscle disease, we also allow a direct caregiver in the group as well. Support, both emotional and physical, along with education is paramount to living well with IBM.

If you have been diagnosed with IBM we hope you will request to join our group on Facebook at www.Facebook.com/groups/inclusionbodymyositis

IBM Patient Video Support Sessions

We also offer a monthly live, online video support session. Meet others face-to-face and discuss topics surrounding life with IBM. Visit our Events page for upcoming sessions.

IBM and other diseases

IBM is not typically associated with an increased prevalence of other diseases such as cancer, interstitial lung disease, or heart disease. Autoimmune disorders such as Sjögren’s syndrome, thrombocytopenia, and sarcoidosis have been reported in up to 15% of patients with sIBM. Life expectancy is not thought to be affected.

Muscle Wasting

The first muscles affected in inclusion body myositis are usually those of the wrists and fingers, and the muscles at the front of the thigh. The muscles that lift the front of the foot also may be affected. This image shows muscle wasting in the forearm into the hands and fingers. 

Muscle biopsy comparison of normal muscle tissue versus muscle tissues affected with Inclusion Body Myositis.  Inclusion Body Myositis is named for the clumps of discarded cellular material — the “bodies” — that collect in the muscle tissues.

Image courtesy of

The Muscular Dystrophy Association

Simply Put

“Simply Put” is a service of Myositis Support and Understanding, to provide overviews of Myositis-related medical and scientific information in understandable language.

MSU volunteers, who have no medical background, read and analyze often-complicated medical information and present it in more simplified terms so that readers have a starting point for further investigation and consultation with healthcare providers. The information provided is not meant to be medical advice of any type.