Which genetic disorder leads to the formation of malformed red blood cells?

Sickle cell disease is a genetic disorder that specifically affects the hemoglobin within red blood cells, causing them to form in a characteristic "sickle" shape rather than their normal, rounded configuration. This abnormal shape of the cells results in reduced flexibility and increased likelihood of blockage in blood flow, leading to pain, anemia, and various complications.

The genetic cause of sickle cell disease involves a mutation in the HBB gene, which codes for the beta chain of hemoglobin. When this mutation occurs, it leads to the production of abnormal hemoglobin known as hemoglobin S. Under low-oxygen conditions, hemoglobin S tends to polymerize, distorting the shape of red blood cells.

In contrast, other options listed either refer to conditions not primarily characterized by the malformation of red blood cells or are related to different aspects of blood health. Anemia generally describes a deficiency in red blood cells or hemoglobin but does not specify a structural malformation. Leukopenia refers to a low white blood cell count, while leukocytosis indicates an elevated white blood cell count; neither of these conditions pertains to red blood cell morphology. Thus, sickle cell disease is uniquely characterized by the presence of abnormally shaped red blood cells due to its genetic