European solidarity is changing the face of rare diseases.

Almost 1 year ago, a BBC fi lm about a teenager called Louisa Ball briefl y captured the imagination of the British public. Called The Real Sleeping Beauty, the fi lm told the story of Louisa and her family as they dealt with the consequences of Louisa’s Kleine-Levin syndrome: a vanishingly rare neurological disorder that causes prolonged episodes of sleep, lasting, in most cases, between 1 and 3 weeks. By focusing on the eff ect that the disorder had on one family, the fi lm makers were able to capture the sense of frustration and isolation caused by a disease about which so little is known that it is impossible to estimate just how rare it is, and, for a short time at least, raise its profi le. But equally, the understandable temptation to focus on the extraordinary stories of individual patients with specifi c rare diseases can obscure a wider truth: that although individuals with any particular rare neurological diseases are—to state the obvious—rare, patients with rare neurological diseases are in fact numerous if they are taken together. And there can be strength in numbers. The European Union defi nes a rare disease as one that aff ects no more than fi ve people in 10 000, although most rare diseases have a prevalence closer to the one in 10 000 mark. However, put all of the estimated 5000–8000 distinct rare diseases together, and between 6% and 8% of the population will experience a rare disease during their lifetime. “If you