Sickled Blood Cell (image) University of California - Berkeley Share Print E-Mail Caption Sickle hemoglobin polymerizes under low oxygen tensions in the tissues, causing the red blood cell to deform. This leads to obstruction in the capillaries and painful episodes for patients. Credit Frans Kuypers: RBClab.com, UCSF Benioff Children's Hospital Oakland Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.