Which of the following is an intrinsic cause of hemolysis?

• A. Sickle cell
• B. Immune-mediated hemolysis
• C. Infection
• D. Hypersplenism

Answer: (A)

Intrinsic causes of hemolysis come from defects inside the red blood cell itself. Sickle cell disease fits here because the primary problem is abnormal hemoglobin (hemoglobin S) within the RBC. When HbS experiences deoxygenation, it polymerizes, making the RBCs rigid and misshapen, which damages the cell and makes it prone to destruction. That destruction occurs independently of external factors, so it represents an intrinsic mechanism.

In contrast, immune-mediated hemolysis involves antibodies or complement attacking RBCs from outside the cell, infection-related hemolysis is caused by external factors such as toxins or immune effects, and hypersplenism destroys RBCs mainly through sequestration and removal by the spleen. These are extrinsic factors acting on RBCs rather than defects inside the RBCs themselves.