Multigene susceptibility to disease.
As the molecular biologists discover more genes which predispose on to diseases the more evident it becomes that some common conditions are associated with more than one gene. What cannot be over emphasised is that these are susceptibilities which not always directly causal. No matter how many predisposing genes one has for obesity , food must be available in luxious amounts to generate fatty tissue.
There are at least seven genetic variants associated with symptomatic coronary heart disease. Three important ones are found on chromosomes 2, 6 and 9 and apparently these account for 38% of coronary heart disease in that population. The paper describing this is from Germany it is possibly different in other populations.
( Rosenzweig A in New Engl J Med 2007, vol 357, August 2nd ; Scanning the Genome for Coronary risk
And Samani N et al New Engl J Med vol 357 August 2nd Genomewide association analysis of coronary artery disease
Another condition or group of conditions with a genetic basis is inflammatory bowel disease. The genes which have been associated with Crohns disease are involved in barrier function and innate and adaptive immunity. There have been 7 and maybe more genes described with a role in this susceptibility or vulnerability.
The current aetiological concepts in the aetiology include the balance between commensal microbes and the immune response of the person. The nature of the host defences is all important. The mucosal barrier is all important.
So we have nice indicators that susceptibility and disease engendering circumstances interplay.
Xavier RJ and Podolsky DK 2007, Unravelling the pathogenesis of inflammatory bowel disease Nature 2007, vol 448, 427-434
- Martin Eastwood