HP and subarachnoid hemorrhage: In the literature, only few data suggest a potential genetic predisposition to vasospasm after subarachnoid hemorrhage and some variants have been detected associated with the occurrence of vasospasm (eNOS, Hp, ApoE, CBS, ENDRA, and SERPINE1) or with its severity (eNOS, PAI-1, ApoE, RyR1, AT2, DDHA1, HMGB1, and ACE) [20, 21].