A 25-year-old woman with hereditary spherocytosis undergoes splenectomy. Her reticulocyte count normalizes and Hb improves, but she now develops thrombocytosis (platelets 900,000/μL) and Howell-Jolly bodies on peripheral smear. What is the mechanism of Howell-Jolly body formation?

• A Failure of nuclear extrusion during erythroid maturation
• B Heinz body formation due to oxidized hemoglobin
• C Parasitic inclusions within red blood cells
• D Retained nuclear remnants (DNA fragments) not cleared by spleen ✓

Explanation

Howell-Jolly bodies are round nuclear DNA remnants (chromatin fragments) that remain in mature RBCs when the spleen is absent (post-splenectomy) or hyposplenic. Normally, the spleen removes these inclusions by pitting. They appear as dense purple dots on Romanowsky stain. Heinz bodies are denatured precipitated hemoglobin (seen in G6PD deficiency/unstable hemoglobins). Cabot rings are mitotic spindle remnants. Post-splenectomy thrombocytosis (transient or sustained) and target cells are also expected.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.