Genetic Variants Explain Podoconiosis
Single nucleotide polymorphisms validated with family-based association testing
WEDNESDAY, March 28 (HealthDay News) -- Genetic variants in the HLA class II region are associated with podoconiosis, a tropical lymphedema resulting from long-term barefoot exposure to soil derived from volcanic rock, according to a study published in the March 29 issue of the New England Journal of Medicine.
Fasil Tekola Ayele, Ph.D., M.P.H., of the National Human Genome Research Institute in Bethesda, Md., and colleagues conducted a genome-wide association study of 194 case patients and 203 controls from southern Ethiopia. Findings were validated by family-based association testing in 202 family trios and HLA typing in 94 case patients and 94 controls.
The researchers found that there was a significant genome-wide association between podoconiosis with the single nucleotide polymorphism (SNP) rs17612858, located 5.8 kb from the HLA-DQA1 locus (in the allelic model: odds ratio [OR], 2.44; in the additive model: OR, 2.19) and suggestive significant associations with seven other SNPs in or near HLA-DQB1, HLA-DQA1, and HLA-DRB1. These associations were confirmed using family-based association testing. HLA typing showed that the alleles HLA-DRB1*0701 (OR, 2.00), DQA1*0201 (OR, 1.91), and DQB1*0202 (OR, 1.79) and the HLA-DRB1*07017-DQB1*0202 haplotype (OR, 1.92) were risk variants for podoconiosis.
"Association between variants in HLA class II loci with podoconiosis (a noncommunicable disease) suggests that the condition may be a T-cell-mediated inflammatory disease and is a model for gene-environment interactions that may be relevant to other complex genetic disorders," the authors write.