Frequently Asked Questions (FAQ)
About Inclusion Body Myositis
MDA Fact Sheet
Questions:
What is IBM? IBM is a slowly progressive inflammatory and degenerative muscle disease that causes painless weakening of specific limb and extremity muscles. The symptoms of the disease usually first appear in those over age 50, but, rarely, can occur in younger persons. Because of some similarities to polymyositis (PM), IBM may be misdiagnosed as treatment-resistant PM. IBM is the most common muscle disease in those over 50, and patients over age 50 who develop a pure form of PM are rare. IBM may also be misdiagnosed as amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease).
What are the symptoms of IBM?
- Muscle weakness that affects the "flexor" muscles of the wrists and fingers (ones that cause the wrist and fingers to bend forward)
- Weakness and visible wasting of the quadriceps muscles (the large muscles on the front part of the thighs)
- Weakness of the lower leg muscles, below the knees
- Weakness of the esophageal muscles, which can cause swallowing difficulty or "dysphagia" (20-40 percent of cases)
- Weakness of other muscle groups as the disease progresses
These symptoms may occur one at a time or appear simultaneously. Together, they can lead to difficulty grasping objects, rising from a sitting position, walking long distances or going up stairs. Weakness of the quadriceps muscles can cause sudden falling, and lower leg weakness can cause difficulty holding the foot up ("foot-drop"), which can lead to tripping. If the esophageal muscles weaken, choking may become a problem when ingesting some types of food or liquids.
What does IBM look like in the muscle? When viewed under the microscope, the muscle cells of persons with IBM contain "vacuoles" (typically, rounded empty spaces). Within the vacuoles there are usually abnormal clumps of several proteins, one of which is amyloid. These characteristic protein clumps, which are called "inclusion bodies," give this disorder its name. In addition, signs of inflammation in the form of invading immune cells are frequently seen in the muscle tissue, but their amount varies, and their lack doesn't rule out a diagnosis of IBM.
How is IBM diagnosed? The definitive way to diagnose IBM is with a muscle biopsy. Electromyography and blood enzyme levels, including creatine kinase, aren't diagnostic.
How does IBM progress? Muscle weakness usually progresses only slowly, and, unlike the progression of polymyositis or dermatomyositis, the course of IBM doesn't tend to fluctuate. Those with the disorder may eventually find that a cane, walker or wheelchair is helpful for traversing long distances, but the disease doesn't seem to affect life expectancy. Sometimes, people with IBM will remain ambulatory for several years. Occasionally, dysphagia symptoms can be severe enough that a nonsurgical expansion of the throat muscles (called "dilation") or a surgical division of specific throat muscles (called a "cricopharnygeal myotomy") may be needed.
How is IBM treated? There currently is no effective treatment for IBM. Unlike the related disorders polymyositis and dermatomyositis, this disorder doesn't respond well to steroids or other immunosuppressant therapies. However, some people may benefit from prednisone treatment, although there's never a full recovery of muscle strength. There is also some evidence that intravenous immunoglobulin (IVIG) may lead to various degrees of improvement in some patients, while others don't respond to IVIG treatment.
Although there's no fully successful pharmacological treatment for IBM, physical therapy can help keep joints mobile, and several options exist to help those who develop dysphagia, ranging from dietary changes to throat muscle dilation to surgery.
What causes IBM? IBM is considered a "sporadic" disease -- that is, there is no evidence that the disease is inherited and researchers don't yet know what causes it. Because of the inflammation associated with the disease, some doctors think IBM is a form of autoimmune disorder. Others speculate that the inflammation is secondary to a different problem in the muscles. For example, some researchers believe that the primary problem in IBM is an age-related inability of the muscle to deal with destructive free radicals and an abnormal accumulation of a number of proteins within the muscle fiber.
Very rarely, IBM with inflammation in the muscle biopsy can be present in families ("familial" IBM). It isn't yet clear whether this form is inherited or whether some people have genes that make them susceptible to whatever causes the sporadic form.
Related Disorders:
Hereditary inclusion body myopathies (h-IBMs): The h-IBMs are genetic diseases that, like IBM, are characterized by muscle weakness and the presence of inclusion bodies, but muscle biopsies don't demonstrate the inflammation common in IBM. Dominant and recessive forms of h-IBM have been identified and linked to particular regions of chromosomes 17 and 9, respectively. Because this disorder is genetic and isn't accompanied by inflammation, it has been labeled inclusion body "myopathy" rather than "myositis." H-IBMs are covered by MDA under the larger category of "distal muscular dystrophies," although these disorders may cause muscle weakness in both distal (away from the trunk) and proximal (near and of the trunk) muscles.
MDA Is Here to Help
The Muscular Dystrophy Association supports research on the causes and disease mechanisms of IBM, and treatment trials. MDA also offers a vast array of services to help those with the disease and their families cope with IBM. Call (800) 572-1717 to find the MDA clinic nearest you, or log in to the Web site at www.mda.org |
