DRD2 and familial hemiplegic migraine: Vulnerability to migraine is inherited, with several genes linked to this: (1) four different missense mutations of the α1A subunit of the P/Q-type voltage-gated calcium channel (chromosome 19) that is responsible for familial hemiplegic migraine (FHM); (2) mutation in gene ATP1A2 (chromosome 1q23) that encodes alpha 2 subunits of Na+/K+ pump will disrupt ATP1A2 allele function; (3) variations within the dopamine D2 receptor gene [9].