Origin and composition of Cabot rings in pernicious anemia.

Cytochemical studies were performed on erythrocytes containing Cabot rings from the peripheral blood of two patients with severe untreated pernicious anemia. These studies demonstrated that the Cabot ring contained arginine-rich histone and non-hemoglobin iron. Structures that may represent precursors of Cabot rings were found in stippled late intermediate marrow megaloblasts. The Cabot ring may result in part from abnormalities in metabolism of both iron and arginine-rich histone that are known to occur in pernicious anemia.