SEM (circa 1970) of a sickle-cell. Sickle-cell disease (SCD) is a group of blood disorders typically inherited from a person's parents. The most common type is known as sickle-cell anemia (SCA). It results in an abnormality in the oxygen-carrying protein hemoglobin (hemoglobin S) found in red blood cells. This leads to a rigid, sickle-like shape under certain circumstances. Problems in sickle cell disease typically begin around 5 to 6 months of age. A number of health problems may develop, such as attacks of pain ("sickle-cell crisis"), anemia, swelling in the hands and feet, bacterial infections, and stroke. Long term pain may develop as people get older. The average life expectancy in the developed world is 40 to 60 years. Sickle-cell disease occurs when a person inherits two abnormal copies of the hemoglobin gene, one from each parent. Magnification: 5000x.