Inclusion body myopathy 2 (IBM2) is an inherited disease that causes a progressive weakening of the legs and arms, typically beginning in the late teens or early 20s and almost always before the age of 40. Typically people with the disease lose the ability to walk 20 years after symptoms appear.
The muscles of the lower leg are typically affected first. As these muscles slowly weaken, walking becomes more difficult and the person’s gait changes. The weakness will spread to the thighs, hand muscles, and certain muscles of the shoulder and neck. A small number of people will also have weakness in the facial muscles. Often the large thigh muscles (quadriceps) are unaffected until late in the course of the disease.
For reasons not well understood, a small number of people who have the genetic mutations that cause IBM2 do not have symptoms of the disease.
IBM2 is most common among Middle Eastern Jews, particularly of Iranian descent. The disease has also been found in small numbers of non-Jews, both within and outside of the Middle East. Roughly 220 individuals with IBM2 have been reported in medical literature, making the disease very rare in the general population.
Studies estimate that among Iranian Jewish communities in Israel and Los Angeles, 1 in 15 people are carriers of mutations that cause IBM2. These studies also estimate that 1 in every 500 to 1000 Iranian Jews in these communities are affected by IBM2.
There is no cure or treatment for IBM2 that can reverse or delay the progression of muscle weakness. Neurologists, rehabilitation specialists, and physical and occupational therapists can aid in relieving symptoms as they appear.
The disease often does not cause noticeable symptoms until the late teens or early 20s when muscle weakness begins. Movement of the arms and legs will become progressively impaired and typically people with IBM2 are wheelchair-bound 20 years after symptoms begin. The disease's effect on lifespan is not well-studied.
A database of genetic information developed at the University of Washington, Seattle and funded by the government's National Institutes of Health. Note that the language of GeneReviews is largely written for medical professionals.
A non-profit organization that supports research into and education about neuromuscular diseases. It is best known for its annual telethon led by entertainer Jerry Lewis.
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