Haemoglobin S

Haemoglobin S (HbS) is a structural defect of haemoglobin due to a point mutation of the beta globin gene.  Under conditions with low oxygen level the mutated beta globin chains cluster together and cause the typical sickle shape of red blood cells (RBCs). Due to this abnormality RBCs become trapped in small blood vessels and spleen. Chronic haemolytic anaemia, bone pain and severe infections are typical clinical signs.  The incidence of HbS coincides with zones where malaria is prevalent. At present, transfusion and an antitumor drug (hydroxyurea) ease the symptoms of sickle cell disorders.

Synonym: Sickle cell disease