Anemias USMLE Step 1 Practice Question
A 31-week neonate presents with generalized edema, respiratory distress, and marked pallor. Prenatal ultrasound demonstrated hydrops fetalis. Vital signs show HR 168/min, RR 62/min, BP 52/28 mmHg, and SpO2 78% on supplemental oxygen. Laboratory studies reveal hemoglobin 7.2 g/dL with hemoglobin electrophoresis showing predominantly hemoglobin Barts. Reticulocyte count is elevated at 12%. No congenital infections are detected. Which genetic abnormality most likely explains these findings?
Answer choices
- ADeletion of all four alpha-globin genesCorrect answer
- BSingle alpha-globin gene deletion
- CTriplet repeat expansion in chromosome 4
- DBeta-globin missense mutation causing valine substitution
- EPoint mutation causing increased hemoglobin oxygen affinity
- FBeta-thalassemia major
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