Immunology USMLE Step 1 Practice Question
A 2 month old boy has recurrent viral and fungal infections, difficulty feeding, and episodes of perioral twitching. He was born with a conotruncal cardiac defect. Physical examination shows low set ears and a small jaw. Laboratory studies reveal hypocalcemia and decreased T cell count. Which embryologic structure most likely failed to develop properly?
Answer choices
- ADorsal pancreatic bud
- BThird and fourth pharyngeal pouchesCorrect answer
- CFirst pharyngeal arch
- DNeural crest migration into the aorticopulmonary septum only
- ESecond pharyngeal arch
- FFifth pharyngeal pouch
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