Sickle-cell disease

Causes and genetics

The condition results from a mutation in the beta-globin gene that gives rise to hemoglobin S (HbS). Sickle-cell disease most commonly occurs when an individual inherits two copies of the mutated gene (homozygous HbSS). People with one normal and one mutated gene (sickle-cell trait, HbAS) usually have few symptoms but can transmit the mutation to offspring. The trait is common in regions that historically had high malaria rates because carriers have some protection against severe malaria.

Clinical features and complications

Typical manifestations include chronic anemia, acute painful episodes called vaso-occlusive crises, and increased susceptibility to infection—especially early in life when the spleen is affected. Over time the disease can cause strokes, chronic kidney disease, pulmonary hypertension, leg ulcers, avascular necrosis of bones, and progressive organ dysfunction. Severity varies widely between individuals and can be influenced by coexisting genetic and environmental factors.

Diagnosis and screening

Diagnosis is established by examining a blood smear and confirming abnormal hemoglobin with tests such as hemoglobin electrophoresis or high-performance liquid chromatography. Newborn screening programs in many countries identify affected infants early so that preventive measures can begin. For an introduction to normal red blood cell form and function see red blood cells; for descriptions of cell shape and deformation see cell morphology.

Treatment and prevention

Management combines symptom control, prevention of complications, and disease-modifying therapies. Common approaches include:

• Hydroxyurea, which raises fetal hemoglobin and reduces crises;
• Regular or episodic blood transfusions to prevent or treat severe anemia and reduce stroke risk;
• Preventive antibiotics and vaccinations to lower infection risk in young children;
• Pain management, hydration, and treatment of acute complications;
• Curative options such as hematopoietic stem cell transplantation in selected patients and emerging gene therapies under investigation.

For authoritative guidance on care and current therapeutic advances consult clinical resources and specialist centers: treatment and resources.

History and public health

Recognition of the disease dates back more than a century; subsequent research established its molecular basis and inheritance pattern. Today it is an important global public‑health issue, particularly in sub-Saharan Africa, parts of the Mediterranean, the Middle East, and India. Public-health strategies emphasize newborn screening, vaccination, access to preventive care, and genetic counseling to reduce morbidity and improve life expectancy.

Notable distinctions

"Sickle-cell disease" is an umbrella term that includes several genotypes (for example HbSS, HbSC, HbSβ-thalassemia) with overlapping but distinct clinical courses. Differentiating sickle-cell disease from sickle-cell trait is important for prognosis, counseling, and family planning.