Leprosy as a genetic model for susceptibility to common infectious diseases.

Leprosy (Hansen's disease) is a human infectious disease that can be effectively treated with long-term administration of multi-drug therapy. In 2006, over 250,000 new cases were reported to the World Health Organization. In the nineteenth century, disagreement among leprologists regarding the hereditary or infectious nature of leprosy was resolved with the identification of the etiological agent, Mycobacterium leprae. However, epidemiological studies maintain the importance of host genetics in leprosy susceptibility. A model free genome-wide linkage scan in multi-case families from Vietnam led to the positional cloning of global genetic risk factors in the PARK2/PACRG and LTA genes. The process of identifying the susceptibility variants provided invaluable insight into the replication of genetic effects, particularly the importance of considering population-specific linkage-disequilibrium structure. As such, these studies serve to improve our understanding of leprosy pathogenesis by implicating novel biological pathways while simultaneously providing a genetic model for common infectious diseases.