Sickle cell disease pathophysiology extends beyond simple vaso-occlusion to encompass sterile inflammation, chronic hemolysis-mediated vasculopathy, and progressive end-organ damage. Free hemoglobin released during intravascular hemolysis scavenges nitric oxide (NO) and generates reactive oxygen species, causing endothelial dysfunction, increased adhesion molecule expression, platelet activation, and a chronic hypercoagulable state. This NO depletion contributes to pulmonary hypertension (present in ~30% of adults with SCD), leg ulcers, priapism, and cerebrovascular disease. Disease-modifying therapies target multiple pathways: hydroxyurea increases HbF, L-glutamine reduces oxidative stress, crizanlizumab blocks P-selectin-mediated adhesion, and voxelotor increases HbS oxygen affinity. The clinician must diagnose genotype-specific complications, prescribe and monitor disease-modifying agents, manage chronic organ damage, coordinate genetic counseling, and direct acute crisis management including exchange transfusion decisions.