Autonomic nervous system involvement in sickle cell disease

Sickle cell disease (SCD) is a genetic disorder of hemoglobin producing hemoglobin-S (HbS) and resulting in recurrent severe episodes of pain, organ damage and premature death due to vaso-occlusion. Deoxy HbS polymerizes, causing red cells to become rigid and lodge in the microvasculature if they do not escape into larger vessels before this transformation occurs. The mechanism that triggers this transition from steady state to vaso-occlusive crisis (VOC) is not known. Patients state that cold, emotional stress, and pain itself can trigger these events. In spite of the connection between these symptoms and the autonomic nervous system (ANS), and the fact that the ANS regulates regional microvascular blood flow, the role of the ANS in sickle pathophysiology has not been significantly investigated. We will briefly review the mechanism of SCD vaso-occlusion, the dysautonomia associated with SCD and sickle trait, and the role that the ANS may play in the genesis of sickle vaso-occlusive crisis.