Recurrent Angio‐oedema without Weals
Angioedema without weals may be either hereditary or acquired. Hereditary angioedema (HAE) is mediated by bradykinin and requires completely different assessment and treatment to acquired mast cell mediator‐induced angioedema. It is inherited as an autosomal dominant disorder. Types I and II are due to mutations in SERPING1, resulting in deficient or non‐functional C1‐esterase inhibitor (C1INH), respectively. HAE with normal C1INH (type III HAE) is associated with gain‐of‐function mutations in F12 in about 20% of patients; no genetic mutation has been identified in the other patients and C1INH is normal. About 10% of patients with chronic spontaneous urticaria will present with mast cell mediator‐induced angioedema without weals, thus it is much commoner than HAE. The assessment and treatment is similar to that for patients with urticaria with weals. Acquired angioedema is mediated by bradykinin when it is due to angiotensin‐converting enzyme inhibitors or C1INH deficiency resulting from consumption of C1INH or its inactivation by autoantibodies. Acquired bradykinin‐mediated idiopathic angioedema, a rare condition, appears to be non‐mast cell mediator induced in a few patients. The entity is poorly defined as there is no diagnostic test but these patients may respond to tranexamic acid.
Keywords angioedema, weals, urticaria, acquired angioedema, hereditary angioedema, histamine, bradykinin