Fine structure of the red pulp of the spleen in hereditary spherocytosis.

The spleens from two children and one adult with hereditary spherocytosis were studied in the electron microscope. Stagnation of the erythrocytes within the splenic cords is attributable to their lack of plasticity as evidenced by the absence of bibbed, tailed, or squeezed forms in transit through the walls of the sinuses. In contrast to the sections studied by conventional light microscopy, the splenic sinuses in hereditary spherocytosis were not “empty,” but contained red blood cells, the majority of which had lost their hemoglobin content. Cordal macrophages were increased in all three cases and were abundant in the splenic cords of the adult patient, causing a further impediment to the rapid passage of erythrocytes. Macrophages, and, to a lesser degree, sinus endothelial cells contained the products of hemoglobin breakdown. The macrophages showed active erythrophagocytosis. Sinus endothelial cells rarely contained intact red blood cells, but showed pronounced pinocytotic activity, a probable mechanism of hemoglobin incorporation. Platelets within the endothelial cells of the sinuses were much more frequently seen in the three cases of hereditary spherocytosis than in control spleens. The presence of ferritin in platelets suggests that they too may play a role in clearing the end products of hemolysis from the spleen.