Rare diseases and expensive drugs

Immunologists/allergists are a physician group that is familiar with caring for patients with rare diseases. Conditions that come under the umbrella of our specialty include various primary immunodeficiency diseases, mast cell disorders, various autoinflammatory diseases and diseases of the complement cascade including Hereditary Angioedema (HAE). A rare or orphan disease is defined by the Europeans as that which occurs in 5 people per 10,000 population. There are 6,000–8,000 known rare diseases with this number growing annually following new discoveries; 5–8% of the population will be affected by a rare disease, 80% of which have a genetic component. While these diseases have a low prevalence, they have a high degree of complexity in either their diagnosis, their management or both. Most are life-threatening or are chronically debilitating. For the individual, these diseases carry special challenges; little is known about them; there is difficulty finding specialists who are knowledgeable; there are very few specific treatments available and when they are, they are very expensive and thus out of reach of the majority of patients. HAE is one rare disease that has received a lot more attention in recent years, mainly because of the registration and marketing of new agents with which to manage the condition. HAE is a rare autosomal dominant disorder with an estimated prevalence of 1:50,000 that has been described in 3 forms; types 1, 2, and 3. Types 1 and 2 result from deficiency in functional C1 inhibitor (C1 INH), either from low absolute levels or production of a dysfunctional protein. In the absence of adequate levels of C1 INH, subcutaneous and submucosal oedema result from the uninhibited action of vasoactive mediators, of which bradykinin is considered the most important. HAE is characterised by recurrent oedema of the limbs, trunk, face, abdomen and sometimes genitals without urticaria, typically taking 24 hours to peak and resolving over 48–72 hours. The most serious manifestation is laryngeal swelling, which was reported in older cohort studies to result in fatal asphyxiation in up to a third of patients. Caring for patients with this condition within Asia Pacific countries poses special challenges. We have no accurate data on patient numbers in individual countries; patients face many obstacles with gaining an accurate diagnosis because of lack of