Smith et al. utilized a convergent functional genomics approach by combining the analysis of a large-scale GWAS with an mRNA expression study to identify polymorphisms in two genes of interest in CFS subjects from the Wichita CFS Surveillance Study.27 Two SNPs were identified in the GRIK2 gene, which codes for an excitatory neurotransmitter receptor that is primarily expressed in the brain. This evidence concerns the gene GRIK2 and myalgic encephalomeyelitis/chronic fatigue syndrome.