出现镰状细胞危象的镰状细胞贫血。当氧分压低时，异常的血红蛋白SS有结晶的倾向，并且RBC变长呈薄的镰刀样形状淤积在毛细血管中，进一步降低血液流动性和氧分压。带有镰状细胞特性（血红蛋白AS）的人并不常发生这种情况。
This is sickle cell anemia in sickle cell crisis. The abnormal hemoglobin SS is prone to crystallization when oxygen tension is low, and the RBC's change shape to long, thin sickle forms that sludge in capillaries, further decreasing blood flow and oxygen tension. Persons with sickle cell trait (Hemoglobin AS) are much less likely to have this happen.
