What is the characteristic RBC shape uniquely associated with HbSS?

The characteristic red blood cell (RBC) shape uniquely associated with HbSS is the sickle cell, also referred to as a drepanocyte. In individuals with hemoglobin S (HbS) due to sickle cell disease, the RBCs undergo a change in shape under certain conditions, particularly when deoxygenated. This causes the cells to become rigid and adopt a crescent-like or sickle shape, which is a defining feature of the disease.

The sickle-shaped cells can lead to various complications, including vaso-occlusive crises due to their impaired ability to traverse narrow blood vessels. The unique deformity of these cells is not only critical for diagnosis but also influences the clinical manifestations of sickle cell disease, as their tendency to cluster and block blood flow can cause pain and organ damage.

Understanding the sickle morphology is essential for hematologists and medical professionals in diagnosing and planning treatment for patients with sickle cell disease.