In sickle cell disease, the primary trigger for vaso-occlusion at the molecular level involves:

• A Polymerization of HbS under deoxygenation, causing cellular dehydration and sickling ✓
• B Oxidative denaturation of hemoglobin at the beta-6 glutamate-to-valine substitution
• C Increased 2,3-BPG causing reduced oxygen affinity with excessive tissue oxygen delivery
• D Complement-mediated hemolysis of sickle erythrocytes in the microcirculation

Explanation

The beta-6 Glu→Val substitution creates a hydrophobic patch on deoxygenated HbS that polymerizes into long rigid fibers, mechanically deforming and stiffening red cells. These sickled, dehydrated cells interact with activated endothelium (through increased P-selectin, VCAM-1), neutrophils, and platelets to cause microvascular occlusion. The mechanism is polymerization-driven (conformational change on deoxygenation), not primarily oxidative or complement-mediated.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.