What is the cause of sickle cell anemia?

Sickle cell anemia is caused by the presence of an abnormal form of hemoglobin known as hemoglobin S. This genetic mutation leads to the production of hemoglobin that, under low oxygen conditions, tends to polymerize (stick together) and forms rigid structures. Consequently, red blood cells deform into a sickle, or crescent, shape. These sickle-shaped cells can become trapped in small blood vessels, obstructing blood flow and leading to various complications, including pain crises and organ damage.

The abnormal hemoglobin is inherited in an autosomal recessive manner, meaning that an individual must receive two copies of the sickle cell gene (one from each parent) to manifest the disease. Those who inherit only one copy typically do not show symptoms but are classified as carriers (sickle cell trait).

In contrast, conditions such as an excess of white blood cells, a deficiency of iron, or an increase in platelet count do not lead to the unique issues associated with sickle cell anemia and are not linked to the genetic basis of the disorder. Therefore, understanding that sickle cell anemia is fundamentally related to the presence of hemoglobin S is crucial for grasping its pathology and implications for affected individuals.