Embryology USMLE Step 1 Practice Question
A 3-day-old male infant presents with respiratory distress and cyanosis. Vital signs show HR 168 bpm, RR 52/min, BP 58/32 mmHg, SpO2 88% on room air. Prenatal ultrasound at 18 weeks revealed a large left-sided fluid collection. Chest X-ray demonstrates mediastinal shift to the right with bowel loops visible in the left hemithorax; no right-sided involvement noted. He denies history of maternal polyhydramnios. Which embryologic defect of the diaphragm is most likely responsible?
Answer choices
- AIncomplete closure of the ventromedial mesentery of the esophagus
- BFailure of the pleuroperitoneal membrane to closeCorrect answer
- CDefective neural crest cell migration to the cardiac outflow tract
- DIncomplete fusion of the muscular ingrowth from the lateral body wall
- EFailure of the septum transversum to develop
- FAbnormal development of the foramen of Morgagni with anterior diaphragmatic hernia
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