tailieunhanh - INFLAMMATORY BOWEL DISEASE - PART 3

Một số nghiên cứu đã so sánh nguy cơ phát triển bệnh viêm ruột ở người thân của bệnh nhân với IBD so với thân các điều khiển. Người ta ước tính 5-10% bệnh nhân có một mức độ đầu tiên liên quan cũng bị ảnh hưởng bởi IBD | 66 Cho dependent on developing a more specific understanding of the earliest stages of pathogenesis. Furthermore reclassification of these disorders based on identification of molecular mechanisms of pathogenesis holds the promise of tailoring medical therapies to individual patients. EPIDEMIOLOGIC EVIDENCE THAT IBD IS A COMPLEX GENETIC DISORDER Several studies have compared the risk of developing inflammatory bowel disease in relatives of patients with IBD compared to relatives of controls. It is estimated that 5-10 of patients have a first degree relative also affected by IBD. IBD is found 15 times more frequently in relatives of CD and UC patients then relatives of normal controls 4 . That familial aggregation is primarily genetic rather than caused by shared environmental etiology such as an infectious agent is suggested by a lack of increased risk to spouses and aggregation occurring among relatives raised separately. The strongest epidemiological evidence for a genetic risk comes from twin studies. In the Swedish twin registry proband pairwise concordance was 44 for Crohn s disease in identical twins and in fraternal twins. The fraternal twin concordance is not much different than the nontwin sibling concordance suggesting that within the same familial environment the closer relationship of fraternal twins is not associated with a substantial increase disease risk. In comparison the proband pairwise concordance for UC in identical twins was 6 as compared to 0 for paternal twins 5 . Taken together this indicates a more significant genetic component for CD compared to UC. These data also show however that inflammatory bowel disease cannot be completely explained by genetics. The lack of complete concordance in identical twins is likely because the unaffected twin not exposed to an environmental trigger or risk factor. Alternatively the presence of a protective environmental affect be contributing. Finally some IBD cases may be primarily a result of .

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