Drepanocitosis

Drepanocitosis, also known as sickle cell disease, is a group of inherited red blood cell disorders caused by mutations in the beta-globin (HBB) gene that produce abnormal hemoglobin S (HbS). The most common form is homozygous HbSS, but variants such as HbSC and HbS/beta-thalassemia occur. HbS tends to polymerize when deoxygenated, causing red blood cells to become crescent-shaped and less flexible, leading to hemolysis and impaired blood flow.

Because the mutant hemoglobin causes red cells to sickle under hypoxia, dehydration, or acidosis, blood vessels can become obstructed, producing painful vaso-occlusive crises and tissue ischemia. Chronic hemolysis leads to anemia and progressive organ damage. The spleen is frequently affected early, increasing risk of infection; over time splenic dysfunction and autosplenectomy are common.

Patients typically experience recurrent pain crises, fatigue, pallor, and jaundice. Infants may have dactylitis. Other complications include acute chest syndrome, stroke, priapism, pulmonary hypertension, renal impairment, leg ulcers, and retinopathy.

Diagnosis relies on newborn screening in many regions, followed by confirmation with hemoglobin electrophoresis or high-performance liquid chromatography showing HbS; genetic testing of HBB may be used. Ongoing surveillance for organ involvement is common.

Management aims to reduce crises and complications. Hydroxyurea decreases vaso-occlusive events and acute chest syndrome; chronic transfusion may be used for disease-specific problems; vaccination and penicillin prophylaxis are important in children. Pain control, hydration, and electrolyte management are essential during crises. Curative treatment with hematopoietic stem cell transplantation is possible in selected patients; gene therapy research is advancing.

With comprehensive care, life expectancy improves but remains reduced compared to the general population, varying with access to medical resources. Prevention includes genetic counseling, carrier screening, and prenatal testing where available. Drepanocitosis is most prevalent among people of African, Mediterranean, Middle Eastern, and Indian ancestry.