The term sickle cell disease (SCD) describes a group of inherited red blood cell disorders. People with SCD have abnormal hemoglobin, called hemoglobin S or sickle hemoglobin, in their red blood cells. Hemoglobin is a protein in red blood cells that carries oxygen throughout the body.“Inherited” means that the disease is passed by genes from parents to their children.ormally, hemoglobin in red blood cells takes up oxygen in the lungs and carries it to all the tissues of the body. Red blood cells that contain normal hemoglobin are disc shaped (like a doughnut without a hole).