In sickle cell disease, the valine-for-glutamic acid substitution at position 6 of the beta-globin chain produces hemoglobin S. Under deoxygenation, HbS molecules polymerize into long, rigid fibers that distort RBC morphology into sickle shapes. These deformed cells adhere to vascular endothelium via adhesion molecules (VCAM-1, ICAM-1, P-selectin), activate the coagulation cascade, and recruit neutrophils—creating a feedforward cycle of vaso-occlusion, ischemia, and reperfusion injury. Chronic intravascular hemolysis releases free hemoglobin, which scavenges nitric oxide (NO), causing endothelial dysfunction, pulmonary hypertension, and stroke risk. The nurse manages comprehensive pain protocols, administers transfusions, monitors for acute complications, coordinates multidisciplinary care, and provides culturally sensitive pain management.