Inclusion body myositis

Inclusion body myositis (IBM) is the most common acquired muscle disease in people over 50, but it is still a rare disease.

What is inclusion body myositis?

Inclusion body myositis (IBM) is a progressive muscle disorder characterised by muscle weakness, inflammation and wasting. It was recognised as a disease in its own right in the 1960s.

IBM progresses slowly and weakness is gradual over months though typically years. Distal muscles (forearm, lower leg and foot) and proximal muscles are affected and muscle wastage follows.

Varying degrees of difficulties swallowing (dysphagia) occur in about half of patients but pain is uncommon.

The disease is progressive by nature, meaning those affected are likely to require a walking aid or wheelchair within 15 years to help conserve energy and stay mobile.

Who gets inclusion body myositis?

IBM occurs more frequently in men than women and is the most common acquired muscle disease in people over 50.

Even so, it is still a rare condition – most general practitioners will not have looked after patients with IBM before, and many doctors will not have heard of the condition.

IBM is rarely found in people younger than 50 years old.

What causes inclusion body myositis?

The short answer is that no one knows. A number of theories have been put forward over the years.

The presence of inflammatory cells in some muscle samples has led to the theory that muscle is damaged by inflammation, caused by a virus or a misdirected immune system. Yet unlike other forms of myositis, efforts to suppress the immune system in those with IBM has not led to clear benefit.

More recently it has been suggested that IBM is primarily a degenerative disease of muscle with inflammation only secondary to this process. Many researchers in several countries continue to accumulate evidence to shed light on the cause of the disease.

In some families IBM is inherited, often with earlier onset than the more common sporadic (non-inherited) form.

What are the symptoms of inclusion body myositis?

All forms of myositis can vary greatly from patient to patient, and few cases are identical or follow the same pattern. Some people may have the disease for months or even years before it is noticed. However, the majority find within weeks they have developed muscular weakness.

The main symptoms of IBM are weak and painful muscles, muscle wasting, tiredness and feelings of depression. IBM progresses slowly and weakness is gradual over months though typically years.

Weak and tender/painful muscles

Distal muscles (forearm, lower leg and foot) and proximal muscles are affected and muscle wastage proceeds. The weakness results in difficulty in walking, lifting arms and getting up from the sitting and lying down positions. Accordingly, patients often notice difficulty with stairs, getting out of a chair and a poor grip. Swallowing muscles are affected in some patients, but most do not encounter severe swallowing problems.

The disease typically does not affect muscles of the heart, eye, gut or bladder. It does not affect the function of the brain or sensation, and speech is rarely affected.

Feelings of depression

Depression and a general feeling of unhappiness is very noticeable and can be an indication of the disease before any sign of muscle weakness.

How is inclusion body myositis diagnosed?

There are a number of pieces of evidence that go together to make the diagnosis of IBM.

Blood test

When muscles are damaged they release a protein into the blood stream called creatine kinase. This can be detected in a routine blood sample. In some people with IBM the level of this protein in the blood is slightly raised. This blood test may therefore alert the physician to the possibility of muscle disease.

Electromyography (EMG)

When healthy muscles contract, they fire off a co-ordinated pattern of electrical impulses that can be detected by a tiny needle positioned in the muscle. When sick muscles contract, abnormal electrical impulses can be detected. However, although EMG may be helpful it cannot make a definite diagnosis.

Muscle biopsy

The definitive test for IBM is a muscle biopsy. The biopsy involves taking a small sample of muscle under local anaesthetic. Laboratory analysis includes a series of stains and reactions, used to highlight different parts of the muscle. In IBM, muscle cells appear damaged. The hallmark of IBM is the inclusion body, which is an abnormal clump of proteins seen in damaged cells.

What treatment is there for inclusion body myositis?

Unlike other forms of myositis, IBM is usually progressive and very difficult to treat.

The presence of inflammatory cells in some biopsies led to suggestions that steroids and other drugs that suppress the immune system might be beneficial in this condition. This immunosuppressant treatment is controversial. Some neurologists are of the opinion that these drugs can give short-term improvement and possibly long-term benefit in slowing the rate of progression, although all agree that these drugs will not prevent muscles from continuing to weaken in the long-term. Other experts argue that any benefits are transient and are outweighed by long-term side effects from the drugs.

Recent trials have studied intravenous infusions of human immunoglobulin (IVIG) in IBM. Results have been contradictory, but provide no firm evidence of enduring benefit. Further trials continue, but currently the costs and side effects do not justify routine treatment of IBM patients with IVIG.

In summary, there is currently no proven treatment. Further research into the cause of the disease will hopefully allow a rational basis to develop effective therapies.

People with IBM may find exercise, physiotherapy and occupational therapy helpful for coping with their condition. Find out more about treatments and therapies

What help is there for those with inclusion body myositis?

Despite the absence of a cure for inclusion body myositis there are a number of therapists who can help.


Physiotherapy and exercise will help to get the most out of weakened muscles. Targeting muscle groups not involved in the disease can also help to keep people with IBM mobile. When walking is affected physiotherapists can advise on walking aids (sticks etc). Physiotherapists can also teach people how to transfer between chairs, beds and wheelchairs if and when they become necessary.

Occupational therapy

Occupational therapists (OTs) can provide advice and equipment to assist in tasks that become increasingly difficult with weakened muscles. More than any other professional they are in a position to provide valuable help in overcoming the everyday practical problems that IBM patients face. Typically they will observe a patient in their own home before advising on strategies, aids and equipment. Examples include cutlery with chunky handles to make gripping easier, aids to help stair climbing and advice on bathing or showering difficulties. OTs are employed in hospitals and by Social Services. Referral to OTs can be made by hospital doctors, GPs or patients themselves through Social Services.

Speech therapy

Speech therapists also have expertise in swallowing difficulties (dysphagia). In some IBM patients weakened swallowing muscles may cause dysphagia. This may cause fragments of food or drink to enter the windpipe resulting in coughing after meals or chest infections. Some IBM patients reduce their intake resulting in significant weight loss. Speech therapists can advise on strategies to help swallowing. Occasionally it is necessary to use other techniques to give adequate nutrition.

Find out more about treatments and therapies

Can I catch inclusion body myositis from other people?

There is no evidence to suggest any form of myositis can be transmitted to other people as an infection.

Unlike other forms of myositis, there is an inherited form of IBM (though not all IBM is inherited). The inherited form appears to be rare in the UK. However, if IBM is of typical age of onset without evidence of similar disease previously in the family, the risk to other members of the family is very small.


Special thanks to Dr S Hammans (Consultant Neurologist) Wessex Neurological Centre and the Muscular Dystrophy Campaign for contributing to the information on this page.

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