Cabot rings

Cabot rings are thin, red-violet staining, threadlike strands in the shape of a loop or figure-8 that are found on rare occasions in red blood cells (erythrocytes).

They are believed to be microtubules that are remnants from a mitotic spindle, and their presence indicates an abnormality in the production of red blood cells.

[1] Cabot Rings, considerably rare findings, when present are found in the cytoplasm of red blood cells and in most cases, are caused by defects of erythrocytic production[2] and are not commonly found in the blood circulating throughout the body.

Cabot rings have been observed in a handful of cases in patients with pernicious anemia, lead poisoning, certain other disorders of red blood cell production (erythropoiesis).

[1] They were first described in 1903 by American physician Richard Clarke Cabot (1868–1939).