Hereditary inclusion body myopathy
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Hereditary inclusion body myopathies
A heterogeneous group of disorders (there are a number of subtypes, they are not all the same), they are also clinically heterogeneous (they present with different symptoms). Generally, neuromuscular disorders characterized by muscle weakness developing in young adults. Disease causes muscle pathology including rimmed vacuoles and filamentous inclusions. Hereditary inclusion body myopathies comprise both autosomal recessive and autosomal dominant muscle disorders that have a variable clinical expression (phenotype) but all share similar structural features.
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[edit] Classification
Types of hereditary inclusion body myopathy currently linked to the GNE gene on chromosome 9 (located at 9p12-p11):
a). An autosomal dominant form (IBM1) where the quadriceps are one of the first muscles to become weak. See OMIN # 603824 :[1]
b). An autosomal recessive form (IBM2), common among people of Middle Eastern and Jewish heritage. This form mainly affects leg muscles, but with an unusual distribution that spares the quadriceps: a so-called quadriceps-sparing myopathy (QSM), the quadriceps are among the last muscles to become weak. See: OMIM # 600737.[2]
c). Nonaka distal myopathy with rimmed vacuoles, essentially a form of IBM2. see: OMIN # 605820: [3]
Another type, inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia (IBMPFD), is linked to a slightly different gene on chromosome 9 (located at 9p13-p12). See: OMIN # 167320 [4]
Another type, inclusion body myopathy-3 (IBM3) is linked to mutations in a gene encoding myosin heavy chain II proteins on chromosome 17 (located at 17p13.1). See: OMIN # 605637 [5]
It would not be a surprise if more types of inclusion body myopathy linked to other genes were identified in the future.
[edit] Genetics
The different forms have different mutations and inheritance patterns. See the detailed OMIN descriptions for details (given above).
[edit] Mechanism
The mechanisms of these diseases are not well understood.
[edit] Treatment
There is no treatment known.
[edit] References
- See OMIN sites listed above.
- See the page on the more common spontaneous related disorder, inclusion body myositis.
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