Anemias USMLE Step 1 Practice Question
A 7-year-old boy with homozygous sickle cell disease presents with fever (39.2°C), lethargy, and malaise. Vital signs show HR 112/min, RR 24/min, BP 98/62 mmHg, and SpO2 98% on room air. Blood cultures grow Streptococcus pneumoniae. Laboratory studies reveal Hgb 7.8 g/dL and WBC 14,500/μL. Abdominal examination shows splenomegaly without hepatomegaly. Which of the following best explains this patient's increased susceptibility to this organism?
Answer choices
- AImpaired neutrophil oxidative burst
- BDeficiency of von Willebrand factor
- CLoss of IgA at mucosal surfaces
- DDefective membrane attack complex formation
- EFunctional asplenia due to repeated splenic infarctionsCorrect answer
- FDecreased production of opsonizing antibodies against polysaccharide antigens
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