Storage cells of spleen and bone marrow in thalassemia: an ultrastructural study.

In the spleens and bone marrows of patients with thalassemia, we have consistently observed PAS-positive histiocytes that contain numerous cytoplasmic bodies surrounded by a single membrane and filled with bundles of fine fibrils (typical thalassemia storage cells). In addition to the characteristic cytoplasmic bod ies, some histiocytes contained leukocytes, erythrocytes, platelets, and plasma cells in different stages of digestion (transitional cells). These findings suggest that the storage cells in thalassemia are macrophages that are unable to metabolize completely the products of phagocytized blood cells. In the spleen the histiocytes were closely associated with plasma cells. When stained by the Giemsa method, the storage cells appeared as ‘sea-blue histiocytes.” The histologic, histochemical, and ultrastructural features distinguish the storage cells of thalassemia from Gaucher’s cells and from storage cells of other disorders in which there is excessive destruction of formed elements of the blood, i.e., chronic myelogenous leukemia and idiopathic thrombocytopenic purpura.