[Rare diseases: a new chapter in medicine].

Rare Diseases (RD) form a new chapter of Medicine which consists of more than 5.000 different diseases. RD have low prevalence (less than 5/10.000), chronic and severe evolution and usually produce serious alteration of quality of life and relationships with physical and social environment. The scarce number of patients with each RD produces very limited interest in research, specially in theraphy. "Orphan drugs" are useful drugs for treating some RD, and in spite of this they are not made because the low number of patients. The particular problem of one RD can be considered not important but as a whole it has great importance, having in mind its consequences over the patient, family and society. It is thought that there are about 20.000 patients in Spain and between 20 and 30 millions in the EU. Care of RD must be multidisciplinary (general practitioners, pediatricians, experts in RD, sociologists and social workers) with a permanent linkage between primary and specialised medicine. An appropriate training of professionals that work with these diseases is needed, as well as to increase and improve the research about RD and to give support to the patients and their families. Global Associations of patients with RD (FEDER in Spain, EURORDIS in EU and NORD in USA) as well as particular associations of some RD (more than 60 in Spain) have developed a very important task to improve health care and social attention about RD and must receive government and social support.