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Decreased C2 and decreased C4
46%
46/99
Decreased C2 and increased C4
7%
7/99
Increased C2 and decreased C4
9%
9/99
Increased C2 and increased C4
18%
18/99
Normal C2 and normal C4
11%
11/99
Select Answer to see Preferred Response
This patient with swelling of the face and extremities after changing medications most likely has angioedema secondary to lisinopril. This disorder will present with decreased serum C2 and C4 complement protein levels. Hereditary angioedema is an autosomal dominant disorder of the complement cascade. It is caused by deficiency of C1 esterase inhibitor, which normally functions to inhibit the kallikrein-kinin pathway. This defect results in activation of bradykinin and resulting vasodilation, vascular permeability, and pain. Notably, angiotensin converting enzyme inhibitors are contraindicated in this disorder because of the risk of facial swelling and respiratory compromise. Hereditary angioedema will have decreased serum C2 and C4 levels on laboratory testing. Treatment of angioedema flares is similar to anaphylaxis with epinephrine, anti-histamines, and fluid replacement. Incorrect Answers: Answers 2-5: These changes in complement levels are incorrect because the main defect in hereditary angioedema is C1 esterase inhibitor. When this enzyme is lacking, non-specific activation of the complement cascade will result in whole body depletion of cascade components such as C2 and C4. Bullet Summary: Patients with hereditary angioedema will have decreased levels of serum C2 and C4 protein.
2.8
(4)
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