Certified Pediatric Hematology Oncology Nurse (CPHON) Practice Exam 2025 - Free CPHON Practice Questions and Study Guide

Sickle Cell Disease (SCD) is primarily caused by a genetic mutation that leads to the substitution of a single amino acid in the beta chain of hemoglobin. Specifically, the mutation involves the replacement of glutamic acid with valine at the sixth position of the beta globin chain, resulting in hemoglobin S (HbS). This altered structure changes the properties of hemoglobin, particularly under low oxygen conditions.

When hemoglobin S releases its bound oxygen, it tends to polymerize, forming rigid structures that distort the shape of the red blood cells into a characteristic sickle shape. These sickled cells are not only less flexible but also have a tendency to clump together, which can obstruct blood flow and lead to various complications associated with SCD.

The other options do not directly result in the sickling of red blood cells. Increased oxygen levels, for instance, would generally stabilize hemoglobin and help maintain normal red blood cell shape. Lack of hydration can contribute to the sickling phenomenon, but it is not the underlying cause of the disease; rather, it can exacerbate the condition. Lastly, increased hemoglobin A levels would typically be associated with normal red blood cell function and would not cause sickling as it is hemoglobin A that does