The frequency and severity of attacks is reduced by oral prophylaxis with attenuated androgens or tranexamic acid, or by regular intravenous infusion of C1INH concentrate[12–14]. However, prophylaxis does not completely abolish attacks. Moreover, many patients cannot benefit from oral prophylaxis because of contraindications, side effects, or lack of efficacy[13, 15, 16]. Immediate access to effective acute treatment is therefore required for all patients.
Replacement therapy with plasma-derived C1INH (pdC1INH) is effective and has been used successfully for over 25 years to attenuate or prevent attacks at all sites [17–19]. More recently, icatibant, a bradykinin receptor inhibitor, and ecallantide, a kallikrein inhibitor, have been shown to be effective at treating attacks[20, 21]. Icatibant was licensed for acute angioedema attacks in patients with C1-inhibitor deficiency in the European Union and several other countries in 2008. Ecallantide was licensed for acute attacks in the USA in 2009. After treatment with either icatibant, ecallantide or C1INH, onset of relief can be expected within 30 to 60 minutes, with full resolution taking a few hours to longer than 24 hours in established attacks[14, 17, 20–23]. Observational studies demonstrate faster relief and reduced attack severity when C1INH is given early [6, 24]. Similarly, icatibant or ecallantide may be more effective when given early, although this is yet to be demonstrated in clinical studies.
The requirement to travel to a medical facility for acute treatment implies at least half a day away from home, school, or work. In the emergency room setting, patients with HAE attacks may not be prioritised over competing emergencies such as patients with heart attacks, stroke or severe injury. This leads to further delay, with increased risk of treatment failure and longer recovery times. Health care staff, unfamiliar with HAE, are reluctant to treat early, when signs are mild or absent, contributing further to the delay and disability. Owing to the reversibility of most attacks, patients themselves may choose to stay at home with symptomatic treatment rather than struggle with access to therapy in the emergency room. This increases absenteeism from work, school, or home responsibilities. For laryngeal attacks, such delay may be fatal. Even where acute treatment is available, it is estimated that only 5-25% of attacks receive definitive treatment (Cicardi, personal communication). Home infusion programmes have been established in centres with an interest in HAE, and have the potential to overcome many of the difficulties associated with health care facility-based treatment[25–28].
Experience shows that access to self or assisted infusion with C1INH reduces severity and duration of attacks, improves HAE-related quality of life, reduces time off work, education or domestic duties, is safe, and is very popular with participants[23–30]. Self infusion is endorsed by the UK, Danish and Canadian-Hungarian consensuses[25, 31–34]. Neither UK nor the Canadian Consensus documents place restrictions on entry to the programme, other than to note that the diagnosis of HAE should be proven, prophylactic therapy optimised (UK document) and that an 'infusion partner' (UK) or 'instruction and support' (Canadian- Hungarian) should be available[27, 31–34]. The Danish home therapy programme considers patients who have more than one moderate or severe attack every 4 weeks, although in practice, these restrictions are relaxed where necessary[25, 27].
The C1 inhibitor deficiency workshop was first held in 1999 in Vizegrád, Hungary and has been a biennial Hungarian event since then. It brings together patients, physicians, nurses, basic and clinical scientists, blood product suppliers and representatives of the pharmaceutical industry with a common interest in HAE and its management. Similarly, the Canadian Hereditary Angioedema Network (CHAEN)/Réseau d'angioedème héréditaire du Canada (RAHC) has organised conferences in 2003, 2006 and 2010, with the aim of developing and updating consensus recommendations for HAE management http://www.haecanada.com. These workshops are attended by experts from all over the world and represent an unprecedented opportunity to pool experience and to share information, with the aim of improving the physical, psychological and economic wellbeing of those affected by HAE. This article summarises consensus opinion, resulting from debates at the Hungarian C1 Inhibitor 2009 Workshop and the Canadian Hereditary Angioedema Network (CHAEN)/Réseau d'angioedème héréditaire du Canada (RAHC) consensus meeting held in Toronto in May 2010 (Appendix 1). Home therapy/self-administration in this article, refers to treatment given in a non-health care setting; given by the patient, a trained relative or friend, outside of a healthcare facility.