Rare Disorders Denmark is an alliance of 48 national patients organisations. Some of the organisations have hundreds of members, whereas others only have a few. Common to them is that they organise people who are born with a serious rare disease or disability.

These "rare" groups face similiar problems: the number of patients is often very small and the diseases unknown. Consequently, little knowledge and awareness of the disorders have been accumulated – neither in the health care sector nor in the social and educational sectors.

Based on the need for an umbrella organisation to speak on behalf of rare disorders, Rare Disorders Denmark was founded in 1985 under the name "KMS". The name was changed in April 2005.