455 Characterization of the Factors Triggering an Edematous Attack in Hereditary Angioedema

BACKGROUND: Hereditary angioedema due to C1-inhibitor deficiency (HAE-C1-INH) is characterized by recurrent attacks of subcutaneous and/or submucosal edema. The mechanisms involved in the development of edematous attacks are being researched extensively and thus, abundant information is available. By contrast, only a few surveys have been conducted on the triggering factors of attacks. METHODS: Data recorded between 2004 and 2010 by 97 HAE patients in their diaries have been analyzed. RESULTS: Eighty-nine of these 97 patients could identify possible factors, potentially related to the onset of attacks. Events associated with an increased propensity for having an attack were physical exertion in 64, mental stress in 53, and mechanical trauma in 53 of these patients. The average number of triggering factors recognized by patients was 2.7 in males and 4 in females. Based on the records of patient diaries, 3176 attacks were diagnosed and patients could identify the triggering factor in 30 per cent of these. The leading provoking factor was mental stress (21%). Analyzing interim distribution during a year showed a higher-than-average number of attacks in March, May, October, and December in almost all the 7 years studied. Clustering of the attacks in March was particularly typical of males and of attacks with an unknown provoking factor. Attacks triggered by stress clustered in the spring and in the autumn. Examining the trigger factors based on the location revealed different patterns among the trigger factors. CONCLUSIONS: According to our results, 92% of patients can identify a factor that triggers an attack – this proportion is higher than that published in the literature. It is important to explore triggering factors, because avoiding these may reduce the number of apparent attacks. Physical exertion was the most common provoking factor. A possible triggering factor could be identified in almost one-third of the attacks. The seasonal clustering of stress-induced attacks shows similarity with the acute exacerbations of psychosomatic disorders. This suggests that psychological support may positively influence the course of the disease.