Red Cell Inclusions

The cytoplasm of all red cells is free of debris, granules, or other structures. Inclusions that find their way into the cytoplasm are the result of distinctive conditions. This section summarizes four of the most common red cell inclusions (Table 3.3): Howell-Jolly bodies, siderotic granules/Pappenheimer bodies, basophilic stippling, and Heinz bodies.

Howell-Jolly bodies are remnants of DNA that appear in the red cell as round, deep purple, nonde-formable structures 1 to 2 pm in size. They are eccentrically located in the cytoplasm and are seen when erythropoiesis is rushed. It is thought that the Howell-Jolly bodies represent remnants of the orthochromic normoblast nucleus as it is extruded from the cytoplasm. The spleen usually pits these inclusions from the cytoplasm, yet when the bone marrow is responding to anemic conditions, the spleen cannot keep pace with Howell-Jolly body formation. In post splenectomy individuals, however, large numbers of Howell-Jolly bodies may be observed, because the spleen is not avail-

44 Part I • Basic Hematology Principles

How Target Cells Are Formed

As a result of artifacts, air-drying and hemoglobin precipitation: Examples: High humidity, slow drying, and hemoglobin C

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