rare disease is defined numbers compiled by Rare Disease UK Raredisease.org.uk http://www.raredisease.org.uk/about-rare-diseases.htm http://www.raredisease.org.uk/about-rare-diseases.htm http://www.raredisease.org.uk/about-rare-diseases.htm 3.5 million in the UK http://www.raredisease.org.uk/about-rare-diseases.htm http://www.raredisease.org.uk/about-rare-diseases.htm rare disease five in 10,000