In sickle cell disease, functional asplenia makes encapsulated bacteria—especially pneumococcus—the classic board-answer for sepsis risk.
A 7-year-old boy with a history of sickle cell anemia presents with 2 days of worsening cough and fever.
He is at increased risk of sepsis from which pathogen?
Answer Options:
A. Streptococcus pneumoniae
B. Shigella
C. Candida albicans
D. herpes simplex virus (HSV)
A common exam pitfall is over-indexing on the current symptoms (cough/fever) instead of the underlying immune deficit. Board items about sickle cell disease often test functional asplenia (from repeated splenic infarctions), which impairs clearance of opsonized encapsulated organisms and raises the risk of rapid, overwhelming bacteremia/sepsis.
Current prevention standards reinforce this: the CDC immunization guidance for altered immunocompetence/asplenia emphasizes vaccination against pneumococcus, meningococcus, and Hib, reflecting the organisms that drive highest-risk invasive disease in this population. ASH guidance likewise centers infection prevention strategies in sickle cell disease (immunizations and early-life antibiotic prophylaxis), with pneumococcus as the archetypal pathogen.
| Option | What It Tests / Implies | Why It’s Wrong Here |
|---|---|---|
| Streptococcus pneumoniae | Encapsulated bacteria causing invasive disease in functional asplenia | Correct: classic cause of overwhelming sepsis in asplenic/functional asplenia patients; target of vaccine strategies (CDC). |
| Shigella | Invasive enteritis/dysentery | Not the classic “asplenia sepsis” organism; not encapsulated and not the board-favored association. |
| Candida albicans | Opportunistic fungal infection (e.g., neutropenia, central lines, broad antibiotics) | Sickle cell disease alone does not create the typical candidemia risk profile being tested here. |
| HSV | Viral infection (encephalitis, neonatal disease, mucocutaneous) | Not the characteristic fulminant sepsis pathogen tied to functional asplenia. |
Functional asplenia (e.g., sickle cell) → think encapsulated bacteria, and the most testable is pneumococcus.
The stem adds respiratory symptoms to distract you into choosing a “pneumonia organism” for the wrong reason. The board-relevant reasoning is immune-function based: functional asplenia → impaired clearance of encapsulated organisms → invasive pneumococcal sepsis risk.
A 6-year-old with HbSS presents with temperature 39.1°C and appears well. What organism is the highest-yield concern for rapid invasive infection?
A child with sickle cell disease is at greatest risk for severe infection because of loss of what splenic function?
Which vaccine is specifically prioritized in patients with anatomic or functional asplenia to reduce risk of overwhelming infection?
A 9-year-old with sickle cell disease develops acute severe leg pain and fever; imaging suggests osteomyelitis. Which pathogen is classically associated?
A 7-year-old with HbSS and a history of splenic sequestration presents with high fever and rigors. Which organism is most concerning?
How would your differential and immediate management priorities differ for fever in (1) a child with sickle cell disease, (2) a child receiving chemotherapy with neutropenia, and (3) a healthy immunized child with the same vital signs?
Q1: Why is Streptococcus pneumoniae the board-favorite organism in sickle cell sepsis questions?
A1: The ABP/board-style expectation is recognition that functional asplenia most strongly predisposes to invasive disease from encapsulated bacteria, with pneumococcus being the classic and historically most lethal pathogen targeted by vaccines.
Q2: Does vaccination eliminate the sepsis risk in sickle cell disease?
A2: No. Boards expect you to know risk is reduced but not eliminated, so fever in sickle cell disease remains high-stakes and typically warrants urgent evaluation/empiric antibiotics per institutional protocols.
Q3: What other encapsulated organisms should I remember with asplenia?
A3: Haemophilus influenzae type b and Neisseria meningitidis are the other high-yield encapsulated organisms highlighted in CDC risk-based immunization guidance for asplenia.
Q4: When is Salmonella most testable in sickle cell disease?
A4: Most commonly as osteomyelitis (and sometimes bacteremia), but when the question is explicitly about “asplenia sepsis risk,” pneumococcus is usually the single best answer.
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