|Rare diseases are defined as diseases with a prevalence of less than 1 per 2,000 persons in the European Union. Some diseases are ‘extremely rare’ and have a prevalence of less than 1 per 50,000. Most rare diseases are chronic and life-threatening or highly debilitating conditions. Approximately 6 to 8 % of the population is affected by a rare disease. If evenly spread, 27 to 36 million Europeans would be affected by a rare disease.
|The number of rare diseases is currently estimated at between 6,000 and 8,000. Due to the rare nature of their condition, patients are often diagnosed very late or not at all and in many cases treatment is not optimal. In addition, the development and distribution of special medicines for a rare disease is not a given. Rare diseases are often very complex and mostly affect several organ systems at the same time. The pathogenesis is not known for all rare diseases and knowledge of the pathology itself, the diagnosis and possible treatment is not widespread and is limited to several (or just one) expert(s) for each rare disease and in some cases is even non-existent.
|Their low prevalence causes specific additional problems. Comprehensive scientific research is often hampered by the size of the patient groups, which are frequently too small. Furthermore the 'return on investment' is rather low for the development of suitable treatments and therefore discouraging for the development of new (orphan) drugs or other forms of therapy. Thus, to date, appropriate treatment is only available for a small fraction of the diseases with an identified molecular cause.
Source: Belgian Plan for Rare Diseases