The most catastrophic abnormal hemoglobin condition are sickle cell anemia and sickle beta thalassemia. In the oxygenated state, HbS functions normally, but when this hemoglobin is deoxygenated, it forms crystal-like rods which deform the red blood cell into a brittle sickle shape. Anemia develops in the first few months of life as production of fetal hemoglobin decreases and production of HbS increases. Enlargement of the spleen results from trapping of sickled red cells in the spleen. If this occurs acutely, severe anemia develops rapidly and transfusions are necessary.
Splenic sequestration can result in death.
Infection may manifest as pneumonia, meningitis, osteomyelitis, septicemia or other infections. Prompt antibiotic therapy can be life-saving. Sickle cell anemia and sickle beta thalassemia affect growth. By about four years of age, height and weight growth rates are slowed. Chronic hemolysis results in a high prevalence of gallstones.