What is a Rare Disease?

Rare DiseaseKey figures

A disease or disorder is defined as rare in Europe when it affects fewer than 1 in 2000.

A disease or disorder is defined as rare in the USA when it affects fewer than 200,000 Americans at any given time.

One rare disease may affect only a handful of patients in the EU (European Union), and another may touch as many as 245,000. In the EU, as many as 30 million people may be affected by one of over 6000 existing rare diseases.

  • 80% of rare diseases have identified genetic origins whilst others are the result of infections (bacterial or viral), allergies and environmental causes, or are degenerative and proliferative.
  • 50% of rare diseases affect children.

Characteristics of rare diseases

Over 6000 rare diseases are characterised by a broad diversity of disorders and symptoms that vary not only from disease to disease but also from patient to patient suffering from the same disease.

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

The fact that there are often no existing effective cures adds to the high level of pain and suffering endured by patients and their families.

Common problems faced

The lack of scientific knowledge and quality information on the disease often results in a delay in diagnosis. Also the need for appropriate quality health care engenders inequalities and difficulties in access to treatment and care. This often results in heavy social and financial burdens on patients.

As mentioned, due to the broad diversity of disorders and relatively common symptoms which can hide underlying rare diseases, initial misdiagnosis is common. In addition, symptoms differ not only from disease to disease, but also from patient to patient suffering from the same disease.

Due to the rarity and diversity of rare diseases, research needs to be international to ensure that experts, researchers and clinicians are connected, that clinical trials are multinational and that patients can benefit from the pooling of resources across borders. Initiatives such as the European Reference Networks (networks of centres of expertise and healthcare providers that facilitate cross-border research and healthcare), the International Rare Disease Research Consortium and the EU Framework Programme for Research and Innovation Horizon 2020 support international, connected research.

How can things change?

Although rare disease patients and their families face many challenges, enormous progress is being made every day.

The ongoing implementation of a better comprehensive approach to rare diseases has led to the development of appropriate public health policies. Important gains continue to be made with the increase of international cooperation in the field of clinical and scientific research as well as the sharing of scientific knowledge about all rare diseases, not only the most "recurrent" ones. Both of these advances have led to the development of new diagnostic and therapeutic procedures.

Rare Disease Day is a great example of how progress continues to be made, with events being held worldwide each year. Beginning in 2008, when events took place in just 18 countries, Rare Disease Day has taken place every year since, with events being held in 94 countries in 2017.

However, the road ahead is long with much progress to be made.

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