Assessment of hereditary angioedema treatment risks

Therapies used for hereditary angioedema (HAE) have been associated with adverse events to include thrombosis, emboli, hepatocellular carcinoma (HCC), exacerbation of attacks, and anaphylaxis. It is difficult to determine incidence of these adverse events from the literature. For this reason we surveyed multiple HAE physicians to determine the risk associated with therapies used in HAE. This study was designed to determine by survey the risk of thrombosis associated with C1-inhibitor (C1-INH), worsening attacks with fresh frozen plasma (FFP), and carcinoma secondary to androgens (mainly danazol). An Internet-based survey was sent to physicians internationally who treat patients with HAE. The survey queried physicians about their observations while treating HAE. Of the 66 physicians who participated in the survey, 37 had patients (856 patients) who were on C1-INH but only 4 (total of 5 patients) had patients on C1-INH who experienced an thromboembolic episode. Of the 17 patients on C1 esterase inhibitor and an indwelling catheter, 3 experienced an embolic, thrombosis, or thromboembolic event. The likelihood of an abnormal event when a patient is on a C1-INH is 5/856 (0.6%), compared with 3/17 (18%) with a central catheter. The incidence of HCC is rare. The incidence of adverse effects to FFP is greater than the literature suggests. Patients with HAE should avoid indwelling catheters, use FFP only when other therapies are unavailable, and use androgens with caution. Most importantly, adverse events to drugs should be reported so that the true incidence of adverse events can be determined.