Some people inherit one sickle cell gene and one other defective hemoglobin gene, resulting in various types of sickling disorders. These disorders range from mild to severe.
Sickle cell disease (hemoglobin SS disease) occurs when both genes produce hemoglobin S. This person typically has symptoms of anemia, mild to life-threatening complications, and a shortened lifespan.
Sickle beta-thalassemia occurs when a person has one hemoglobin S gene and another gene that causes the body to produce less hemoglobin than normal. This person may have mild to severe sickle cell disease.
Hemoglobin SC disease occurs when a person has one hemoglobin S gene and one abnormal hemoglobin C gene. This person may have generally milder symptoms and a longer lifespan than a person with sickle cell disease but still may become seriously ill.
Hemoglobin SE disease occurs when a person has one hemoglobin S gene and one abnormal hemoglobin E gene. This person may have mild anemia. Most people do not have symptoms.
Hemoglobin SO disease and hemoglobin SD disease occur when a person has one hemoglobin S gene and one abnormal hemoglobin O or hemoglobin D gene. This person may experience all sickle cell disease symptoms, ranging from mild to severe.
Natarajan K, et al. (2010). Disorders of hemoglobin structure: Sickle cell anemia and related abnormalities. In K Kaushansky et al., eds., Williams Hematology, 8th ed., pp. 709-741. New York: McGraw-Hill.
Wang WC (2009). Sickle cell anemia and other sickling syndromes. In JP Greer et al., eds., Wintrobe's Clinical Hematology, 12th ed., pp. 1038-1082. Philadelphia: Lippincott Williams and Wilkins.
ByHealthwise Staff Primary Medical ReviewerE. Gregory Thompson, MD - Internal Medicine Donald Sproule, MDCM, CCFP - Family Medicine Adam Husney, MD - Family Medicine Martin J. Gabica, MD - Family Medicine Specialist Medical ReviewerMartin H. Steinberg, MD - Hematology