Rare diseases are an heterogeneous set of human pathologies whose common features are the low frequency rate in the population (under 5:10,000, according to European criteria) and serious social and health problems associated with such a low frequency. Their number involves a consistent part of the population (approx. 6,000). These pathologies are little known and studied, often chronic and crippling, for which social and health interventions must include support for life and work choices to persons affected. Important public health initiatives are underway at both the national and international levels.only subscribers can see the full article