Immunology USMLE Step 1 Practice Question
A 23 year old woman comes to the emergency department with recurrent episodes of severe abdominal pain and swelling of the lips and tongue. She has no urticaria or pruritus. Symptoms have not improved with antihistamines or epinephrine during prior episodes. Laboratory studies show low C4 levels. Which of the following is the most likely underlying problem?
Answer choices
- AExcess histamine release from mast cells due to IgE cross linking
- BDeficiency of terminal complement proteins
- CAutoantibodies against desmoglein 3
- DPreformed recipient antibodies against donor antigens
- EDeficiency of C1 esterase inhibitor leading to increased bradykininCorrect answer
- FDeficiency of C3 convertase regulatory proteins leading to uncontrolled complement activation
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