Heritability seems to be more eminent in MwA subtype than MwoA, further supported by the identification of mutations in three ion transporter genes (CACNA1A, ATP1A2, and SCN1A) associated with familial hemiplegic migraine (FHM); a rare monogenic form of MwA (19). The gene discussed is CACNA1A; the disease is familial hemiplegic migraine.