What is a major inherited blood disorder characterized by abnormal hemoglobin?

Sickle cell disease is indeed a major inherited blood disorder characterized by abnormal hemoglobin, which is a key protein responsible for carrying oxygen in the blood. In sickle cell disease, the hemoglobin (known as hemoglobin S) has a mutation that causes red blood cells to take on a sickle or crescent shape, particularly under low oxygen conditions. This abnormal shape leads to various complications, including pain crises, increased risk of infection, and hemolytic anemia, due to the abnormal cells' propensity to rupture more easily.

The condition is inherited in an autosomal recessive manner, meaning that an individual needs to inherit two copies of the mutated gene, one from each parent, to manifest the disease. Carrier individuals, known as sickle cell trait, typically do not experience the disease's severe symptoms but can pass the gene onto their offspring.

Other disorders listed, such as hemophilia, thalassemia, and iron deficiency anemia, do not share the same hallmark of abnormal hemoglobin as the defining feature. Hemophilia is primarily a bleeding disorder due to clotting factor deficiencies, thalassemia is also characterized by abnormal hemoglobin but involves a different mechanism than sickle cell disease, and iron deficiency anemia is related to insufficient