[Rare diseases. Concept, epidemiology and state of the question in Spain].

Rare diseases are those whose prevalence is below 5 cases per 10,000 inhabitants in the European Community. Most cases are diagnosed during paediatric age due to their genetic origin, while some others are congenital malformations. Nevertheless, a higher prevalence is seen during adulthood as most of the former diseases are very severe and patients die during childhood. At the same time, higher survival rates are related to some chronic rare diseases in adults. The Spanish Network of Research Epidemiology for Rare Diseases (REpIER) developed the first atlas showing the geographical distribution of rare diseases in Spain, assessed the Spanish rare disease registries, contributed to the further development of regional plans on rare diseases, as well as to social and health actions, and established the real group of needs to be solved. These have been included in the Communication of the European Commission on Rare Diseases as well as in the Spanish Senate Presentation.