Codocytes (target cells) are the most common RBC morphologies encountered in the double heterozygous state known as hemoglobin SC disease (Hb SC). Hb SC red cells are often dehydrated and become xerocytes (cells that have their hemoglobin pooled to one side).
Some red cells that contain hemoglobin C crystallize as they dehydrate. A hemoglobin C crystal is indicated by the arrow in the top image on the right. In Hb SC disease, some red cells may take on both the sickle shape and the shape of hemoglobin C crystals, forming a Hb SC crystal (indicated by the arrow in the bottom image on the right).