The abnormal sickle-shaped RBCs are damaged or destroyed as they pass through the circulatory system. The anemia usually has many noticeable effects on the person with this disease. It can cause a condition called sickle cell crisis. The crisis may occur under certain conditions such as altitude or pressure changes, low oxygen, or some illnesses. In sickle cell crisis the RBCs become even more deformed and block tiny blood vessels, causing acute, prolonged pain and other complications.
Thalassemias are a group of inherited anemias caused by abnormal hemoglobin.
The abnormal hemoglobin may cause abnormal red blood cells as well as low hemoglobin levels. Thalassemias most commonly affect people of Mediterranean descent, but some types also affect peoples of Africa, Asia, India, and the South Pacific. Most forms of thalassemia are mild, but some forms cause disease in children and may result in death before adulthood. People who have thalassemia should not take iron medication. Mild anemia usually does not produce symptoms.