Sickle cell shape and structure: images and concepts (1840-1980).

I. First observations of "crescentic particles" in animals. II. The first five descriptions of sickle shaped red cells in man. III. Relationship of sickling to the state of oxygenation of the hemoglobin. a) Forerunners: the sickling is reversible. b) Discoverers: sickling as result of asphyxia. IV. Sickle cell trait ("latent sickling"). V. Presence of hemoglobin rod-like structures in sickle cells. a) Indirect evidence. b) Observation of the surface of the cells by electron-microscope shadow casting technique. c) Electron microscopy of the interior of the cells. VI. Irreversible sickle cells. VII. Heterogeneity of sickling disorders. a) Association with other hemolytic anemias. b) Non-Hb S sickling. c) Factitious sickle cell shapes. VIII. Myelin forms and agglutination of sickle-cells. IX. Sickle cell shapes. a) Drepanocytes: mechanism of formation. b) Discodrepanocytes (holly-leaf forms). c) Echino-drepanocytes. d) Stomato-drepanocytes. e) Sphero-drepanocytes.