Sample: Serum, Plasma
Range: 19 - 59 mg/dL
Remarks: A marked decrease of C1 esterase inhibitor is seen in patients with hereditary angioneurotic edema. Usually these patients also have low Complement C4 but Complement C3 remains within normal range. Adquired angioedema is produced by non hereditary C1 Esterase deficiency (drug induced, allergenic deficiency or SLE associated). Increased C1 Esterase may be associated with an inflammatory process (see CRP).