Histaminergic Angioedema: Similarities and Differences Between Isolated Angioedema and Chronic Urticaria with Angioedema

It is not clear if histaminergic angioedema is a form of chronic urticaria or is a different entity belonging to a subtype of acquired angioedema. We performed a prospective study comparing clinical features, biomarkers and autoimmune mechanism of 70 patients with histaminergic angioedema without hives (IH-AAE) and 64 patients with chronic urticaria presenting hives and angioedema (CSU-AE). Men ratio in CSU-AE was 0.28 whereas was 0.44 in IH-AAE. We did find significant differences in angioedema location. Lips and eyelids angioedema was significantly more frequent in CSU-AE (95,2% lips, 73% eyelids)(p=0.002) than in IH-AAE (78,9% lips, 53,5% eyelids); on the contrary, lingual angioedema was significantly more frequent in IH-AAE (57,7%) than in CSU-AE (30,2%). None of the patients had laryngeal edema nor needed intubation or tracheotomy. No significant differences in any sera CSU biomarker measured was found. IgE levels were similar in both entities within normal values. Basopenia was only found in CSU-AE with significantly lower basophil number (0,031±0,031) than in IH-AAE (0,046±0,03)(p=0.001). Likewise, we found that 31,15% of CSU-AE patients’ sera induced basophil activation, whereas none of the IH-AAE sera were able to. Only one patient inducing 6,88% of activation slightly over the 5% cut-off value. Although very similar, there are several features that distinguish IH-AAE from CSU-AE were identified. Apart from gender distribution and affected areas, two of the key CSU features which are basopenia and the sera ability to activate normal basophils were not present in IH-AAE, suggesting a different mechanism and cell implication.