What are Rare Diseases?

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What are Rare Diseases?

Rare diseases are diseases which affect a small number of people compared to the general population (less than 1 person per 2000). However, while these diseases are rare, around 300,000 people in Ireland are living with a rare disease and this can have a big impact on people’s health and the health service.

Rare Diseases at a glance

400M

Estimated that 400 million people globally have a rare disease¹

50%

50% of those with a rare disease are children^1-3

6,000+

To date 6000-7000 rare diseases have been identified^2,3

5 Years

It takes on average 5 years from first visit to a healthcare professional to receive an accurate diagnosis¹

95%

95% of rare diseases do not yet have treatments²

¹ https://globalgenes.org/learn/rare-disease-facts/
² https://rarediseases.org/wp-content/uploads/2014/11/NRD-1008-RareInsights_v1.pdf
³ https://www.nature.com/articles/s41431-019-0508-0

72% of rare diseases are genetic which means that the cause may be traced back to mutations (changes) in a gene. Genes carry the information that determines your traits, which are features or characteristics that are passed on to you — or inherited — from your parents.

Most rare diseases of genetic origin occur randomly as the baby develops in the womb, while some are inherited from one or both parents who are carriers of the gene mutation. The exact cause for many other rare diseases remains unknown. Environmental factors, such as diet, smoking, or exposure to chemicals and infections also can play a role in rare diseases.

Examples of rare diseases related to environmental factors include uncommon types of anaemia caused by vitamin-deficient diets or certain medications. A rare cancer caused by environmental factors is mesothelioma, which affects the cells lining the chest space. More than 90% of mesothelioma cases are caused by exposure to asbestos, a fibrous mineral once widely used in fireproofing and insulation materials.

Since so few people are affected by rare diseases, the number of medical experts can be small, the care available to patients may be inadequate and research may be limited. This means that for some, it may take years for them to be diagnosed with a rare disease and that researchers need to work together to find new treatments.

The Rare Disease Clinical Trial Network supports researchers to connect with international experts and bring more clinical trials to Ireland for rare diseases. We work with local and international partners to support patients by providing information about relevant clinical trials and how they can get involved in this research.

Useful links

If you or someone you know has recently been diagnosed with a rare condition, please visit the following sites to find out what supports are available for you: