What classifies a disease as rare

:: About rare diseases

What is a rare disease?

'Rare diseases' are those disorders that only affect a comparatively small number of people. In Europe, a disease is classified as rare if it affects at most one in 2000 people. The 'rare' status can change over time or regionally. Thalassemia, a genetic form of anemia, is rare in Northern Europe but common in Mediterranean countries. There are also diseases that are common everywhere in their main forms, but rarely occur in special forms.


How many rare diseases are there?

There are thousands of rare diseases. Six to seven thousand rare diseases have already been found, and new rare diseases are regularly described for the first time in the medical literature. The number of existing rare diseases also depends on the specificity of the classification of rare entities / diseases. In medicine, a health disorder with a circumscribed configuration of symptoms and a uniform treatment is delineated as a particular disease. Such a delimitation depends on the sharpness of the analytical procedure. The more differentiated our investigation, the more differences we can see between individual cases of illness. This fact is reflected in the different classifications made available by Orphanet.


What are the characteristics of rare diseases?

Almost all genetic disorders are rare diseases, but not all rare diseases are genetic diseases. For example, there are very rare infectious diseases, rare forms of autoimmune disorders or rare cancers. The causes of most rare diseases have not yet been clarified.

Rare diseases are serious, often chronic, and progressive diseases that are often life threatening. In many rare diseases, the first symptoms can appear shortly after birth or in early childhood (e.g. proximal spinal muscular atrophy, neurofibromatosis, osteogenesis imperfecta, chondrodysplasia or Rett syndrome). In over 50% of rare diseases, the disease does not manifest itself until adulthood (e.g. Huntington's disease, Crohn's disease, Charcot-Marie-Tooth disease, amyotrophic lateral sclerosis or Kaposi's sarcoma).


What are the medical and social consequences of the rare diseases?

Medical and scientific knowledge of rare diseases is nowhere near sufficient. The topic of 'rare diseases' has long been neglected by doctors, politicians and scientists, so that until recently neither suitable health policy nor scientific measures existed. There is no effective therapy for most rare diseases, but adequate care measures can improve the quality of life and also increase life expectancy. For the treatment of certain diseases such. Some impressive progress has been made, which should motivate us to intensify research efforts and to further strengthen social solidarity.

Rare disease patients tend to face similar problems. Difficulties exist mainly with regard to the diagnosis, the availability of relevant information and the placement of suitable specialists. Equally important are access to qualified specialist facilities, general social and medical support, effective cooperation between hospitals and general practitioners, professional and social integration or the preservation of independence. Those affected are often exposed to psychological, social, economic or cultural problems. Difficulties of this kind could be prevented by sensible regulations. Many patients are not diagnosed as a rare disease is often not recognized due to a lack of adequate scientific and medical knowledge. It is precisely this group of patients that is exposed to the greatest suffering, as they are denied access to appropriate support.


Will rare disease diagnosis and treatment improve?

In terms of a basic understanding of rare diseases, science can certainly provide some answers. Today hundreds of rare diseases can be detected with a simple biological test. For some of the diseases, it was possible to expand knowledge about the natural course of the disease through the creation of registers. The formation of networks promotes the exchange of knowledge and leads to an improvement in research efficiency. The overall perspective has improved, as changes in legislation and national efforts in many European countries have created new foundations for combating rare diseases.


What measures in Europe are dealing with rare diseases?

A description of the European approach to rare diseases and orphan drugs can be found on the European Commission's website:


A description of the current national initiatives in Europe, and an overview of the incentives created so far by the European Commission and the European Community, is available on the website of the European Committee of Experts on Rare Diseases (European Union Committee of Experts on Rare Diseases) available:



How do I get information about a specific disease?

Orphanet maintains a directory of rare diseases and provides information on over 6,000 of these diseases. The database also provides information on specialized service offers from the participating countries of the Orphanet consortium.