Embryology USMLE Step 1 Practice Question
A 2-month-old girl is brought to the emergency department with severe respiratory distress (RR 60/min, SpO2 76% on room air) and cyanosis. Physical examination reveals bilateral cleft palate, micrognathia, and poor feeding. The infant requires emergent intubation. Subsequent echocardiography demonstrates truncus arteriosus (a single arterial trunk arising from the heart with a single semilunar valve overriding a ventricular septal defect). Genetic testing and fluorescence in situ hybridization (FISH) for 22q11 microdeletion are negative. Which of the following embryologic processes is disrupted to account for both the craniofacial and cardiac findings in this patient?
Answer choices
- AFailure of neural tube closure in the hindbrain region
- BAbnormal migration and differentiation of neural crest cells in the conus cordis and pharyngeal archesCorrect answer
- CDefective endocardial cushion tissue formation at the atrioventricular canal
- DFailure of somite segmentation in the occipital region
- EIncomplete regression of the first pharyngeal pouch
- FInadequate mesodermal proliferation during primary palatal formation
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