The genetics of leprosy

Population and family distributions of leprosy in the Bogia Subprovince of Papua New Guinea have been examined for evidence of inherited susceptibility to the disease. Evidence for multigenic inheritance of leprosy severity is provided by the restriction of pleiotropy with red-cell enzyme 6PGD phenotypes to a single clinical form of leprosy and by the superior fit of pedigree data to a multifactorial, rather than single-gene model, of inheritance. Discrimination of the multifactorial model as superior to the single-gene model in testing the mode of inheritance of quasi-continuous multiple threshold traits was possible by extending the models to incorporate information on assortative mating for leprosy. Leprosy epidemiological patterns simulated blood genetic marker gene frequency distributions of 13 polymorphic loci in their dependence on linguistic and distance effects. In an analysis of leprosy prevalence rates in 25 languages, leprosy rates corresponded more closely with linguistic similarity than with geographic proximity, suggesting the importance of ancestral genetic relationships between groups as a determinant of similarity in between-group leprosy susceptibility.