What is a rare disease?

The facts

  • The European Union considers a disease as rare when it affects less than 1 in 2,000 citizens.
  • Rare diseases currently affect 3.5% - 5.9% of the worldwide population, an estimated 30 million people in Europe and 300 million worldwide. 
  • Over 6,000 different rare diseases have been identified to date.
  • 72% of rare diseases are genetic whilst others are the result of infections (bacterial or viral), allergies and environmental causes.
    • 70% of those genetic rare diseases start in childhood.

Reference: Estimating cumulative point prevalence of rare diseases: analysis of the Orphanet database, European Journal of Human Genetics (September 2019)

The impact

Rare diseases are characterised by a wide diversity of symptoms and signs that vary not only from disease to disease but also from patient to patient suffering from the same disease.

Due to the low prevalence of each disease, medical expertise is rare, knowledge is scarce, care offerings inadequate and research limited. Despite their great overall number, rare disease patients are the orphans of health systems, often denied diagnosis, treatment, and the benefits of research.

Relatively common symptoms can hide underlying rare diseases leading to misdiagnosis and delaying treatment. Typically disabling, the quality of life of a person living with a rare disease is affected by the lack or loss of autonomy due to the chronic, progressive, degenerative, and frequently life-threatening aspects of the disease.


Rare diseases not only affect the person diagnosed - they also impact families, friends, care takers and society as a whole.

Read more:
>> Estimating cumulative point prevalence of rare diseases: analysis of the Orphanet database

>> Press release: New scientific paper confirms 300 million people living with a rare
disease worldwide (September 2019)

Page created: 19/08/2009
Page last updated: 21/07/2020