HP and subarachnoid hemorrhage: Current interest is driven by recent studies suggesting that Hp phenotypes, primarily associated with different affinities to bind free hemoglobin and affinity of the hemoglobin-Hp complex to its receptors, may be associated with differential outcomes in subarachnoid hemorrhages (Chaichana et al., 2007, 2010; Leclerc et al., 2015) and that Hp may play an important role in the development of secondary injuries, particularly delayed arterial vasospasm and brain ischemia (Nonaka et al., 1979; Borsody et al., 2006).