To understand sickle cell disease, you first need to understand what healthy red blood cells do. Red blood cells are small, flexible, disc-shaped cells that flow easily through blood vessels, picking up oxygen from the lungs and delivering it to every tissue in the body. Their round shape and flexibility are what allow them to squeeze through even the tiniest blood vessels without getting stuck. In someone with sickle cell disease (SS genotype), the haemoglobin inside the red blood cells is abnormal. Under certain conditions — when the body is dehydrated, cold, stressed, or low on oxygen — these abnormal haemoglobin molecules stick together and cause the red blood cell to change shape. Instead of a smooth, flexible disc, the cell becomes rigid and crescent-shaped, like a sickle tool. This is where the disease gets its name. Sickled cells cause two major problems. First, they block blood vessels. Because they are stiff and irregularly shaped, they can clump together and obstruct the flow of blood. When blood cannot reach a tissue, that tissue is starved of oxygen — and this causes intense, sudden pain. These episodes are called sickle cell crises, and they can last hours or days and affect any part of the body: the chest, joints, abdomen, and bones. Second, sickled cells die faster than normal red blood cells. Healthy red blood cells live for about 120 days. Sickled cells often last only 10 to 20 days. The body cannot replace them fast enough, which leads to chronic anaemia — a persistent shortage of healthy red blood cells. Nigeria has the highest number of people with sickle cell disease of any country in the world. Approximately 150,000 children are born with the condition in Nigeria every year. This is not a rare disease in this context — it is one of the most common serious inherited conditions affecting Nigerians, and understanding it is important for everyone, not just those directly affected.