Inclusions within red blood cells composed of denatured hemoglobin
They are formed as a result of oxidative damage or mutations (i.e G6PD)
Macrophages in the spleen remove the denatured hemoglobin giving rise to the classic “bite cells” (see below)
Nuclear (basophilic) inclusions within RBCs
Normally: During maturation, after leaving the bone marrow, erythroblasts’ nuclei are expelled within the spleen
HOWEVER, in patients without a spleen (asplenia) secondary to (i.e surgery, radiation or sickle cell disease) will retain these remnants (see below)
REFERENCES
Hutchison HE, Ferguson-Smith MA. THE SIGNIFICANCE OF HOWELL-JOLLY BODIES IN RED CELL PRECURSORS. Journal of Clinical Pathology. 1959;12(5):451-453.
Mathew H, Dittus C, Malek A, Negroiu A. Howell-Jolly bodies on peripheral smear leading to the diagnosis of congenital hyposplenism in a patient with septic shock. Clinical Case Reports. 2015;3(8):714-717. doi:10.1002/ccr3.323.
Winterbourn CC, Carrell RW. Studies of Hemoglobin Denaturation and Heinz Body Formation in the Unstable Hemoglobins. Journal of Clinical Investigation. 1974;54(3):678-689.
Webster, Stewart. Heinz Body Phenomenon in Erythrocytes. Blood 1949 4:479-497