Findings suggest that the Haptoglobin 2-2 genotype is critical for the development of severe vasospasm, which typically occurs 24 hours after SAH in mice ¹⁾.

Hp2-2 mice formed aneurysms that were significantly larger and had a significantly greater number of macrophages in the aneurysm wall compared with Hp1-1 mice. This suggests that the proinflammatory state associated with the Hp2-2 protein is involved in aneurysm formation and that the Hp genotype may be a useful biomarker in predicting aneurysm progression ²⁾.

Hp 2-2 genotype was an independent predictor of CSW after subarachnoid hemorrhage. Because CSW is strongly associated with delayed cerebral ischemia, the use of Hp genotype testing requires more investigation, and larger prospective confirmation is warranted. Additionally, a more objective definition of CSW needs to be delineated ³⁾.