This inherited blood disorder has defective hemoglobin and crescent-shaped red blood cells. What is the condition?

• A. Hemophilia
• B. Sickle cell anemia
• C. Thalassemia
• D. Leukemia

Answer: (B)

The main idea here is recognizing an inherited blood disorder where abnormal hemoglobin makes red blood cells deform into a crescent or sickle shape. In this condition, a mutation in the beta-globin gene produces hemoglobin S. When oxygen levels drop, HbS tends to polymerize, twisting and hardening the cells into crescent-shaped forms. These misshapen cells don’t flow well and are destroyed more quickly, causing anemia and episodes of blocked blood flow that lead to pain and organ issues. It’s inherited in an autosomal recessive pattern, meaning a person needs two copies of the mutated gene to have the disease.

Hemophilia, by contrast, is a bleeding disorder caused by deficiencies in clotting factors, not red blood cell shape. Thalassemia involves problems with producing normal hemoglobin chains and typically presents with anemia but not the classic crescent-shaped cells. Leukemia is a cancer of white blood cells, which affects blood counts and immune function rather than RBC shape.