Many rare diseases have a genetic cause and although almost all genetic diseases are rare, not all rare diseases have a genetic origin. For example, there are also very rare infectious diseases, rare autoimmune diseases, rare allergies and rare forms of cancer. The cause of many rare diseases still remains unknown.
Characteristics of rare diseases:
- They are often serious, chronic and progressive conditions and often multi-systemic, hence involving multiple organ systems.
- For many rare diseases, symptoms are already noticeable at birth or become evident in childhood, while others do not become apparent until adulthood.
- Variation of rare diseases can be observed across geographic areas, due to population genetic diversity, environmental or social aspects.
- For most diseases there is a lack of knowledge on prevalence and epidemiological data.
Rare diseases are diseases with a high burden and are emerging as a public health priority in Europe due to the above described characteristics. Read more about the European policy on rare diseases.