This study aimed to understand better primary AE, the clinical characteristics, and the possible therapeutic approaches. Angioedema (AE) is a non-pitting, non-itching swelling of skin or mucosa. The symptom can become life-threatening if located in the airways. Primary (monosymptomatic) AE is a manifestation of several different diseases, and the diagnosis is not always straight-forward. The aetiological and pathophysiological factors of primary AE are not entirely clarified. There is a need for further investigation. This was a retrospective cohort study of patients referred to an outpatient dermatology clinic in a tertiary care hospital for clinical assessment due to primary AE from 1996 to 2014.

A total of 315 patients were identified with primary AE. The most frequent subtype was idiopathic AE (42.5%), and the second most common was angiotensin-converting enzyme-inhibitor (ACEi)-induced AE (31.1%). Three patients were diagnosed with hereditary AE, and one patient was diagnosed with acquired C1-inhibitor deficiency. At least 107 (34.0%) patients had established histaminergic AE. More than 1/3 of the patients were treated in an emergency room or hospitalized due to AE. 98.1% of patients had experienced AE in the head and neck area. Seven patients required acute airway intervention. Six of these had ACEi-induced AE. Female sex and smoking were found to be risk factors for developing AE.

The most frequent diagnoses were histaminergic-, non-histaminergic idiopathic AE and ACEi-induced AE, whereas complement C1-inhibitor deficiency was rare. Histaminergic AE made up a substantial group of patients with primary AE. Even though AE has different pathophysiological causes, many cases have overlapping clinical manifestations, making the diagnosis and treatment difficult.