Sickle cell anaemia is an inherited blood disorder caused by a genetic mutation in the HBB gene, which results in the production of abnormal hemoglobin (Hemoglobin S). This abnormal hemoglobin causes red blood cells to lose their flexible, disc-like shape and become rigid and crescent or sickle-shaped. Because these cells are stiff and sticky, they get stuck in narrow blood vessels, hindering the free flow of blood and oxygen to tissues and organs, which leads to episodes of severe pain known as crises.

A. haemophilia: This is a heritable bleeding disorder where the blood does not clot properly due to a lack of blood-clotting proteins. It does not involve a change in the shape of red blood cells.

B. albinism: This is a genetic condition characterized by a lack of melanin pigment in the skin, hair, and eyes. It is not a blood disorder and does not affect red blood cell morphology.

C. colour blindness: This is a hereditary condition that affects the ability to distinguish between certain colours due to defects in the cone cells of the retina. It has no effect on red blood cells or blood flow.