What is a rare disease?

Rare diseases are diseases that affect a small number of people compared to the general population, and their rarity causes specific problems. In Europe, a disease is considered rare if it affects less than 5 people in 10 000. A disease may be rare in one region but common in another. There are also many common diseases whose variants are rare

How many rare diseases are there?

There are thousands of rare diseases. To date, six to seven thousand rare diseases have been discovered, and new diseases are regularly described in the medical literature.

What are the origins and characteristics of rare diseases?

While almost all genetic diseases are rare diseases, not all rare diseases are genetic diseases. There are also very rare forms of infectious diseases, such as autoimmune diseases and rare forms of cancer. For many rare diseases, the cause is still unknown. Rare diseases are serious, often chronic and progressive diseases. In many rare diseases, symptoms can be seen at birth or in childhood. However, more than 50% of rare diseases do not appear until adulthood.