Sickle Cell Anemia

Sickle cell disease (SCD) refers to a group of hemoglobinopathies that include mutations in the gene encoding the beta subunit of hemoglobin. The first description of SCA 'like' disorder was provided by Dr. Africanus Horton in his book The Disease of Tropical Climates and their treatment (1872). However, it was not until 1910 when Dr. James B Herrick and Dr. Ernest Irons reported noticing 'sickle-shaped' red cells in a dental student (Walter Clement Noel from Grenada). In 1949, independent reports from Dr. James V Neel and Col. E. A. Beet described the patterns of inheritance in patients with SCD. In the same year, Dr. Linus Pauling described the molecular nature of sickle hemoglobin (HbS) in his paper 'Sickle Cell Anemia Hemoglobin.' Ingram Vernon, in 1956, used a fingerprinting technique to describe the replacement of negatively charged glutamine with neutral valine and validated the findings of Linus Pauling.

Within the umbrella of SCD, many subgroups exist, namely sickle cell anemia (SCA), hemoglobin SC disease (HbSC), and hemoglobin sickle-beta-thalassemia (beta-thalassemia positive or beta-thalassemia negative). Several other minor variants within the group of SCDs also, albeit not as common as the varieties mentioned above. Lastly, it is essential to mention the sickle cell trait (HbAS), which carries a heterozygous mutation and seldom presents clinical signs or symptoms. Sickle cell anemia is the most common form of SCD, with a lifelong affliction of hemolytic anemia requiring blood transfusions, pain crises, and organ damage.

Since the first description of the irregular sickle-shaped red blood cells (RBC) more than 100 years ago, our understanding of the disease has evolved tremendously. Recent advances in the field, more so within the last three decades, have alleviated symptoms for countless patients, especially in high-income countries. In 1984, Platt et al. first reported the use of hydroxyurea in increasing the levels of HbF. Since then, the treatment of sickle cell has taken to new heights by introducing several new agents (voxelotor, crinzalizumab, L-glutamine) and, most recently, gene therapy.