Leprosy and the natural selection for psoriasis
Received 19 July 2011; Accepted 21 October 2011. Available online 12 November 2011.
Abstract
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.
Article Outline
- Introduction
- Hypothesis
- Evidence that psoriasis was selected to resist leprosy
- Leprosy affects fecundity and can act as selection pressure for a relatively frequent phenotype
- Mechanisms of leprosy resistance in psoriasis
- A paleoepidemiologic consequences of the present hypothesis: did psoriasis contribute to the decline of leprosy in medieval Europe?
- Evaluation of the hypothesis
- Conflict of interest
- Funding source
- References
