Hereditary inclusion body myopathy

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Hereditary inclusion body myopathies (HIBM) are a group of rare genetic disorders which have different symptoms. Generally, they are neuromuscular disorders characterized by muscle weakness developing in young adults. Hereditary inclusion body myopathies comprise both autosomal recessive and autosomal dominant muscle disorders that have a variable expression (phenotype) in individuals, but all share similar structural features in the muscles.

HIBMs are a group of muscle wasting disorders that are uncommon in the general world population. One autosomal recessive form of HIBM is known as IBM2 or GNE myopathy, which is a common genetic disorder amongst people of Iranian Jewish descent.^[1] IBM2 has also been identified in other minorities throughout the world, including those of Asian, European, and South American, and Middle Eastern descent. In Japan and other East Asian countries, this disorder is known as distal myopathy with rimmed vacuoles (DMRV).

IBM2 causes progressive muscle weakness and wasting. Muscle wasting usually starts around the age of 20 – 30 years, although young onset at 17 and old onset at 52 has been recorded. It can progress to marked disability within 10 to 15 years, causing many people with IBM2 to become full-time wheelchair users. The weakness and severity can vary from person to person. In some, weakness in the legs is noticed first. In some others, the hands are weakened more rapidly than the legs. IBM2 does not seem to affect the brain, internal organs or sensation. The quadriceps are relatively spared, and remain strong until the late stages of disease, which is the reason IBM2 is often referred to as quadriceps sparing myopathy (QSM).