A 21-year-old woman comes to the office due to recurrent episodes of self-limited, colicky abdominal pain. She also had an episode of facial swelling that resolved spontaneously. The patient has no other significant past medical history and takes no medications. Examination is unremarkable. Evaluation shows that her complement protein C1, even when not attached to an antigen-antibody complex, is excessively cleaving C2 and C4. Which of the following is most likely increased in this patient?

Question

A 21-year-old woman comes to the office due to recurrent episodes of self-limited, colicky abdominal pain.  She also had an episode of facial swelling that resolved spontaneously.  The patient has no other significant past medical history and takes no medications.  Examination is unremarkable.  Evaluation shows that her complement protein C1, even when not attached to an antigen-antibody complex, is excessively cleaving C2 and C4.  Which of the following is most likely increased in this patient?

Quizplus · Accepted Answer

Eductional Objective: C1 inhibitor (C1INH) deficiency causes increased cleavage of C2 and C4 and results in inappropriate activation of the complement cascade.  C1INH also blocks kallikrein-induced conversion of kininogen to bradykinin, a potent vasodilator associated with angioedema

A 21-Year-Old Woman Comes to the Office Due to Recurrent