Complement 1 esterase inhibitor (C1-INH) deficiency or hereditary angioedema is caused by the deficiency or malfunction of C1-INH and results in angioedema and episodes of abdominal pain and vomiting. C1-INH deficiency can be either acquired or hereditary. An initial C1-INH workup includes testing for C1-INH and complement 4 (C4) levels.
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