A 14-year-old girl with sickle cell disease is admitted to the hospital due to fever for 2 days. Temperature is 38 C (100.4 F), blood pressure is 120/80 mm Hg, pulse is 120/min, and respirations are 18/min. Examination shows no abnormalities. Laboratory studies reveal:
| Complete blood count | |
| Hemoglobin | 10 g/dL |
| Mean corpuscular volume | 86 µm3 |
| Reticulocytes | 2% |
| Platelets | 240,000/mm3 |
| Leukocytes | 14,000/mm3 |
Blood cultures are obtained, and appropriate pharmacotherapy is initiated. Her peripheral blood smear is shown in the exhibit. The smear findings indicated by the arrow most likely reflect which of the following processes?
Show Explanatory Sources
This patient's peripheral smear shows a Howell-Jolly body, a dark-purple remnant of a red blood cell (RBC) nucleus that is normally removed by the spleen. In patients with asplenia, which can be anatomic (eg, splenectomy) or functional (eg, sickle cell disease [SCD]), Howell-Jolly bodies are not removed from circulation and are therefore present on peripheral smear. This patient also has sickle-shaped RBCs and polychromasia (indicative of reticulocytosis) on peripheral smear, consistent with her underlying SCD.
A point mutation in the beta-globin gene causes sickling of RBCs and the classic manifestations of SCD, including hemolytic anemia and vasoocclusive episodes. Recurrent infarction from the poorly deformable RBCs in the splenic vasculature leads to progressive splenic dysfunction with functional asplenia by age 5 in most patients.
Because splenic macrophages are critical in the immune response against encapsulated bacteria (eg, Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis), patients with SCD are at increased risk of potentially fatal infection. Therefore, fever (with or without leukocytosis) in the setting of SCD warrants hospitalization and empiric antibiotic therapy.
(Choice A) Bone marrow suppression can occur in patients with SCD and parvovirus (eg, aplastic crisis). Expected laboratory findings include acute anemia and absent reticulocytes. This patient's hemoglobin level and mild reticulocytosis (due to chronic hemolysis) are typical of SCD at baseline.
(Choice B) Unlike in this patient, peripheral smear abnormalities with intraerythrocytic parasites include trophozoites (ring forms) in malaria and babesiosis. In addition, both conditions would present with anemia relative to the patient's baseline.
(Choice C) Peripheral smear in leukemia shows circulating blasts, immature cells with a large nucleus and scant cytoplasm. In addition, abnormalities in two cell lines (eg, leukocytosis and thrombocytopenia) are usually seen.
(Choice E) Toxic granulations are purple cytoplasmic granules in the periphery of neutrophils (not RBCs) that are typically seen with infection.
Educational objective:
Howell-Jolly bodies on peripheral smear reflect splenic dysfunction, which occurs in sickle cell disease due to recurrent infarction of the splenic vasculature. Functional asplenia increases the risk of invasive infection with encapsulated organisms.