Sickle cell disease
Sickle cell disease is a group of inherited blood disorders that cause red blood cells to become misshapen, leading to anemia, pain, and potential organ damage.
Overview
Sickle cell disease affects hemoglobin, the molecule in red blood cells that delivers oxygen to the body. People with this disease have atypical hemoglobin molecules called hemoglobin S, which can distort red blood cells into a rigid, sickle, or crescent shape.
Symptoms
Signs and symptoms typically begin in early childhood and include:
- Anemia: A low number of red blood cells, causing fatigue, shortness of breath, and delayed growth.
- Painful episodes: Occur when stiff, sickled red blood cells get stuck in blood vessels, depriving tissues and organs of oxygen.
- Jaundice: Yellowing of the skin and whites of the eyes due to the rapid breakdown of red blood cells.
- Infections: Individuals are prone to repeated infections.
- Organ damage: Long-term deprivation of oxygen can damage the lungs, kidneys, spleen, and brain.
- Pulmonary hypertension: High blood pressure in the vessels supplying the lungs, which can lead to heart failure.
Causes
Variants in the HBB gene cause sickle cell disease. This gene provides instructions for making beta-globin, a component of hemoglobin. In sickle cell disease, at least one beta-globin subunit is replaced by hemoglobin S. In the most common form, sickle cell anemia (HbSS disease), hemoglobin S replaces both beta-globin subunits.
Inheritance
Sickle cell disease is inherited in an autosomal recessive pattern. This means both copies of the HBB gene in each cell must have a variant to cause the disorder. Parents of an individual with the condition each carry one copy of the altered gene but typically do not show signs or symptoms of the disease.