sickle cell anemia. an inherited condition in which red blood cells and hemoglobin molecules do not form properly. the resultant red blood cells are crescent or sickle shaped and have a tendency to rupture creating a clogging and clotting problem.ickle cell anemia. an inherited condition in which red blood cells and hemoglobin molecules do not form properly. the resultant red blood cells are crescent or sickle shaped and have a tendency to rupture creating a clogging and clotting problem.