A 3-year-old boy with sickle cell anemia is brought to the emergency department due to fever. He has chills but no bone pain, cough, or difficulty breathing. The patient's medical history includes hospitalization as an infant for dactylitis and again last summer for splenic sequestration crisis. Other than ibuprofen and acetaminophen for fever and pain, he takes no medications regularly and his vaccinations are current. Temperature is 39.5 C (103.2 F), blood pressure is 78/40 mm Hg, pulse is 140/min, and respiratory rate is 22/min. Physical examination shows a lethargic boy with mild pallor. Laboratory results are as follows:
Hematocrit 24% Platelets 325,000/mm3 Leukocytes 18,800/mm3 Neutrophils 80% Bands 13%
Blood culture is pending. Which of the following organisms is the most likely cause of this patient's condition?
Sickle cell disease | |
Pathophysiology |
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Clinical features |
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Laboratory |
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Management |
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HbA = hemoglobin A; HbS = hemoglobin S; RBCs = red blood cells. | |
This patient's fever, chills, hypotension, leukocytosis, and bandemia are consistent with sepsis. Intermittent sickling of red blood cells in the spleen leads to splenic infarction and ultimately functional asplenia. As a result, patients with sickle cell disease (SCD) are at high risk for sepsis from Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis.
The incidence of bacteremia has decreased as a result of improved vaccination approaches (eg, pneumococcal conjugate and polysaccharide vaccines, meningococcal conjugate vaccine). Despite vaccination, S pneumoniae remains by far the most common cause of sepsis in patients with SCD, usually from non-vaccine serotypes. Therefore, patients with SCD should receive prophylactic penicillin until at least age 5. Unfortunately, this patient was not taking penicillin.
(Choices A and B) H influenzae and N meningitidis are encapsulated organisms that can cause sepsis in patients with SCD; however, they are extremely rare in vaccinated patients. In contrast, S pneumoniae remains a common cause of sepsis despite immunization due to non-vaccine serotypes.
(Choice C) Pseudomonas aeruginosa is a common cause of bacteremia in patients with burn wounds and neutropenia. It is an unusual cause of sepsis among patients with SCD as the majority of P aeruginosa isolates are not encapsulated.
(Choices D and E) Salmonella species and Staphylococcus aureus are the 2 most common causes of osteomyelitis in patients with SCD. However, this patient has no bone pain suggestive of osteomyelitis, and neither organism is a common cause of sepsis.
Educational objective:
Sickle cell disease (SCD) causes functional asplenia due to recurrent splenic infarction. Therefore, patients are at risk of overwhelming infection with encapsulated organisms and should receive vaccination and penicillin prophylaxis. Pneumococcus remains the most common cause of sepsis in patients with SCD.