| Re: hereditary? -- arlene1 | |||
| Posted by Bill Tillier ® , 2008/03/30, 21:17:03 | Post Reply | Top of Thread | Main Forum |
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from my website:
* Most people develop a form called sporadic inclusion body myositis (sIBM) that is not inherited from parents and is not passed on to children. When we think about genetic diseases, we generally think of mutations occurring in a particular gene that causes some sort of illness. No such genetic defect has been detected and directly linked to sporadic inclusion body myositis. In contrast, there are exceedingly rare forms of IBM (myopathy) that are described below, that are linked to specific genetic mutations and that are inherited. However, when it comes to the sporadic variety, it is likely that there is a genetic predisposition. It's important to realize that different individuals and different groups of people show slightly different combinations of genes. Groups of people from different ethnic backgrounds and from different geographical locations will share distinctive genetic ancestry that differs from groups of people from different areas and different backgrounds. Research on the genetics of sporadic inclusion body myositis has uncovered a group of genes that are present in about 70% of the cases tested. This cluster of genes has also been associated with higher incidences of several other autoimmune disorders such as rheumatoid arthritis. This group of genes is most common in Caucasian people with Northwestern European ancestry. A couple of other signs point to a genetic predisposition in sporadic IBM. One sign is that in a few rare cases, sIBM is seen in brothers and sisters within the same generation. This is called familial IBM and is mentioned below. Finally, the fact that there are several forms that are definitely genetic (although exceedingly rare) that are very similar to the sporadic type are an indication that there likely is some sort of genetic interaction somewhere in the sporadic form as well. Research on other diseases has indicated that genetic predispositions often inter-act with environmental variables. Thus, if an individual possesses this cluster of around 200 genes there will be a complex interaction between these genes and between the genes and environmental factors ("triggers.") It is possible that one of the environmental factors is aging and that as the cells become older and less effective at repairing themselves the disease may more easily take root. Another possibility is that a virus may be an environmental trigger, without the genetic predisposition, the virus would not cause IBM but when given the right combination of genes plus the virus, sIBM may be more likely to develop. In summary, there may be a pattern of genes involved in creating a susceptibility to getting sIBM but this particular combination of different genes would not likely be passed on to children, therefore, while sIBM may be influenced by a person's genetic makeup, this form is not considered an inherited disease per se. * Familial IBM is associated with the typical features that are seen in sIBM, but occurs in siblings in the same generation. The familial occurrence of such a rare disease highlights the importance of genetic predisposition in the etiology and pathogenesis of sIBM. see Needham (2007). * One category of IBM illnesses, the hereditary inclusion-body myopathies (hIBM) are linked to specific genetic defects and are inherited; they are passed down from generation to generation. To date there is no indication that the genes responsible for these conditions are involved in sIBM. Related link: http://members.shaw.ca/btillieribm/ |
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