One gene not found in the leading edge overlap, GRIK2, has been linked to CFS [44, 45, 52] and two further genes, PIK3RI and PRKAR1A, are also members of the enriched BioCarta pathways that have previously been linked to fatigue in CFS [44–47]. Here, GRIK2 is linked to myalgic encephalomeyelitis/chronic fatigue syndrome.