New York State Department of Health - Wadsworth Center - Cytohematology Proficiency Testing

Slide 138 [100X]        Click here for a higher resolution image.

The red cell inclusion is a Cabot ring (code: 32). Cabot rings are red-purple staining threadlike filaments in the shape of a ring or figure 8 in the red blood cell, often in association with basophilic stippling. They may also appear as granules in a linear array rather than as complete rings. Cabot rings are thought to be microtubules from a mitotic spindle or remnants of the nuclear membrane. Cabot rings are seen in severe anemia including megaloblastic anemia, leukemia and lead poisoning. They are distinguished from the ring forms of Plasmodium by their larger size and by the absence of a red chromatin mass (Miale, J B: Laboratory Medicine Hematology 6th ed.,CV Mosby Co.,1982, p.488).

The presence of target cells and basophilic stippling in this image also makes the identification of parasite (code: 54) an unlikely choice. The peripheral smears of most patients with malarial inclusions are normochromic and normocytic . About 25% of patients with malaria exhibit hemolytic anemia - characterized by spherocytosis (due to pitting of parasites from the red cell), reticulocytosis and shortened red blood cell survival.

Due to a lack of participant consensus, pass credit was issued for this image.

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