Table 1.

Differential diagnostic components for workup of patients with unexplained recurrent angioedema [16]

Urticaria	Family history	C1INH, C4	Responsive to antihistamines	Onset > 40, low C1q	FXII genetic mutation	Diagnosis
Yes						Mast cell-mediated or idiopathic angioedema
No	Yes (75% of cases)	Lowa	No			HAE-C1INH
No	Yes or No	Normalb	Yes			Idiopathic histaminergic angioedema
No	No	Normalb	No			Idiopathic non-histaminergic angioedema
No	Yes	Normalb	No		Yes	HAE-FXII
No	Yes	Normalb	No		No	HAE-U
No	No	Lowa	No	Yes		Acquired C1INH deficiency

C1INH C1 inhibitor, HAE hereditary angioedema, HAE-C1INH hereditary angioedema due to C1 inhibitor deficiency, HAE-FXII hereditary angioedema with F12 mutation, HAE-U hereditary angioedema, unknown

^aLow (< 50% of normal) C1INH antigenic levels and/or low (< 50% of normal) functional C1INH activity (low C4 levels and normal antigenic C1INH levels should prompt functional C1INH activity assessment)

^bNormal C1INH antigenic levels and C1INH functional activity