What blood component primarily clogs the vessels during a vaso-occlusive crisis?

During a vaso-occlusive crisis, the primary issue arises from the behavior of abnormal red blood cells, particularly in conditions like sickle cell disease. These abnormal red blood cells have a rigid and sickle-shaped appearance, which makes them less flexible compared to normal red blood cells. As a result, they can become trapped in small blood vessels, leading to occlusion or blockage.

This blockage disrupts normal blood flow, causing pain and potential tissue damage due to oxygen deprivation in the affected areas. It's important to note that normal red blood cells have a biconcave shape which allows them to deform easily and navigate through narrow blood vessels, reducing the likelihood of occlusion. Other components, such as plasma proteins and white blood cells, may also play a role in the overall response to a vaso-occlusive crisis, but it is the abnormal red blood cells that primarily contribute to the mechanical blockage of the vessels.