Erythrocyte inclusions are elements that may be present in red blood cells (RBCs). The appearance, composition, and associated physiology of the inclusions are specific for each type of inclusion. Identification and reporting of these inclusions are important because their presence may indicate diseases or disorders.
One of the functions of the spleen is pitting, which refers to its ability to pluck out particles in red blood cells without destroying them. The presence of red blood cell inclusions in a peripheral blood smear can indicate an increased amount of inclusionary bodies, so much that the spleen can not keep up by removing them all. This is where the presence of red cell inclusions may indicate a disease state. Additionally, if a person has had a splenectomy, there may be an increased amount of red blood cell inclusions observed on a peripheral blood smear.
Many erythrocyte inclusions can be visualized on a Wright-stained smear. However, some erythrocyte inclusions can only be observed by using a special stain. For example, to confirm the presence of Heinz bodies, hemoglobin H bodies, or reticulocytes, smears must be prepared after staining an aliquot of fresh whole blood with a supravital stain such as new methylene blue or brilliant cresyl blue. The image on the right is a peripheral blood smear prepared after staining the blood sample with a supravital stain; Heinz bodies, which are clumps of precipitated hemoglobin, are indicated by the arrows.
To detect siderosomes, a stain must be used that is specific for iron, such as Prussian blue.
