A 16-year-old boy with sickle cell disease presents with fever, cough, and dyspnea. Blood smear examination reveals the structure marked **B** in the diagram. Which of the following best explains the presence of this finding in sickle cell disease?

Explanation

## Why "Functional asplenia due to autosplenectomy from repeated vaso-occlusive infarction of splenic tissue" is right Howell-Jolly bodies (marked **B**) are basophilic intracytoplasmic nuclear DNA remnants that are normally removed by splenic macrophages through a process called "splenic culling." Their presence in mature RBCs indicates an absent or dysfunctional spleen. In sickle cell disease, repeated vaso-occlusive crises cause infarction of splenic tissue, leading to autosplenectomy (functional asplenia) by adolescence. This loss of splenic function prevents the removal of Howell-Jolly bodies, allowing them to persist in circulating RBCs. This finding is pathognomonic for functional asplenia and explains the patient's increased susceptibility to encapsulated bacterial infections (pneumococcal sepsis), which is a major cause of morbidity and mortality in sickle cell disease. (Robbins 10e Ch 14) ## Why each distractor is wrong - **Impaired splenic macrophage function from chronic hemolysis and iron overload**: While chronic hemolysis and iron overload do occur in sickle cell disease, the primary mechanism for Howell-Jolly body persistence is loss of splenic tissue itself through autosplenectomy, not functional impairment of remaining macrophages. The spleen is largely destroyed, not merely dysfunctional. - **Congenital absence of the spleen from abnormal embryological development**: Asplenia is not congenital in sickle cell disease; the spleen is present at birth but becomes fibrotic and non-functional over time due to repeated infarction. This is an acquired process, not a developmental anomaly. - **Splenic sequestration of sickled RBCs leading to splenic enlargement and dysfunction**: Early in sickle cell disease, the spleen may be enlarged due to sequestration of sickled cells, but this leads to splenic infarction and fibrosis, not persistent enlargement. By adolescence, the spleen is atrophic and fibrotic (autosplenectomy), not enlarged. **High-Yield:** Howell-Jolly bodies = functional asplenia; in sickle cell disease, autosplenectomy occurs by adolescence due to repeated vaso-occlusive infarction, predisposing to life-threatening pneumococcal sepsis. [cite:Robbins 10e Ch 14]