[Rare diseases: the role of internal medicine]

Rare diseases, defined in the European Union as conditions affecting fewer than five per 10,000 inhabitants, often manifest themselves in childhood, but are playing an increasingly important role in internal medicine due to the significantly improved long-term prognosis and a number of diseases that primarily occur in adulthood. Although noteworthy structures already exist nationally and internationally (networks, registers, databases, self-help groups), awareness of these diseases in daily routine and knowledge of the partly divergent care structures must be improved. There are no specific treatments for many of these diseases, but drugs are increasingly being developed-particularly in oncology-that are subject to special orphan drug status.