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GENETIC EPIDEMIOLOGY
When considering the etiology of a disease, it is important to account for genetic susceptibility as well as environmental factors. Because of advances in molecular and genetic techniques, epidemiologic studies have expanded to include use of biologic samples. Upon completion of the Human Genome Project in 2003 and the International HapMap Project in 2005, researchers were able to use a technique known as the genome-wide association study (GWAS). This method examines the association between disease and single nucleotide polymorphisms (SNPs), markers for groups of DNA variation inherited together in blocks (haplotypes). Findings from these studies can be used to investigate the molecular pathways of disease. One can look for associations in a hypothesis-driven or non-hypothesis-driven manner.
A study by Petukhova et al. illustrates the use of GWAS techniques to explore the pathogenesis of alopecia areata (AA). Using genetic samples from 1054 cases and 3278 controls, they identified 139 SNPs significantly associated with AA (P โค 5โรโ10โ). They found an association between these SNPs and the genomic regions containing several genes that control the activation of T cells and cytokine production.
The results of the study implicated both innate and acquired immunity in the pathogenesis of AA and suggested potential autoimmune mechanisms for this condition.