PATHOGENESIS OF AUTOIMMUNE DISEASE
Genetic, enviromental and random (stomachastic) factors all play a role in the pathogenesis of autoimmune diseases. Family members of affected individuals are at higher risk for developing autoimmune disease than the general populations. The relative risk to siblings of affected individuals (probands) versus the risk in the general population is a useful way to estimate the importance of genetic factors. The relative risk is between five and fiftyfold higher in siblings of affected probands than in unrelated individuals in most autoimmune diseases. Part of this effect is accounted for by MHC-linked genes.