02202nas a2200313   4500000000100000008004100001260003400042653004000076653003800116653002200154653001100176653002100187653001200208653003900220653002600259653001500285653001400300653002100314653002300335653002400358100001600382700001500398700001600413245005300429300001100482490000700493520137400500022001401874       2012                            d  c2012 JanbElsevieraNew York 10aEuropean Continental Ancestry Group10aGenetic Predisposition to Disease10aHistory, Medieval10aHumans10aImmunity, Innate10aleprosy10aMitogen-Activated Protein Kinase 310aModels, Immunological10aPrevalence10aPsoriasis10aReceptor, erbB-210aSelection, Genetic10aToll-Like Receptors1 aBassukas ID1 aGaitanis G1 aHundeiker M00aLeprosy and the natural selection for psoriasis.  a183-900 v783 a<p>Psoriasis is a genetically determined, almost worldwide-distributed inflammatory skin disease with overall higher prevalence among people of northern European ancestry. Since enhanced innate immunity is an important feature of the pathophysiology of this disease, it has been proposed that differences in the prevalence of psoriasis in different populations mainly result from differences in natural selection for gene polymorphisms associated with more vigorous immunity against infectious agents. However the infectious agent(s) that could have acted upon human population as selection pressure for psoriasis is still obscure. Based on the remarkable clinical observation that psoriasis and leprosy are almost mutually exclusive, a fact that is further supported by divergent HLA patterns in patients with psoriasis and leprosy we propose that "resisting leprosy" may have been the evolutionary advantage that favoured the expansion of some psoriasis-associated genotypes especially in the progenitors of modern Europeans. Moreover, we suggest that the spreading out of a certain genetic resistance trait may offer a supplementary explanation for the better understanding of the relatively rapid decline of leprosy in the late medieval epoch in Europe. Both genetic and paleoepidemiologic methods could be employed in order to challenge the present hypothesis.</p>  a1532-2777