Panel A provides a graphical overview of the CYP2C gene locus containing CYP2C18, CYP2C19, CYP2C9, and CYP2C8. The latter is encoded on the reverse strand (arrow) while the other three genes are encoded on the forward strand. CYP2C19 is composed of nine exons, covering 92.9 kb. Rare whole and partial gene deletion events that include at least exon 1 of the CYP2C19 gene have been designated by PharmVar as CYP2C19*36 and *37, respectively. Whole gene deletions may include the neighboring CYP2C gene(s) and even extend beyond the CYP2C gene locus. Partial deletions affect different regions of CYP2C19 and may affect CYP2C18 and/or 2C9 as well. Panel B summarizes the core sequence variations defining CYP2C19*2 through*10 and *17.