Rare Disease Day

What is a rare disease?

Rare diseases are diseases which affect a small number of people compared to the general population and specific issues are raised in relation to their rarity.

Rare diseases are serious, often chronic and progressive, diseases. For many rare diseases, signs may be observed at birth or in childhood, as is the case of proximal spinal muscular atrophy, neurofibromatosis, osteogenesis imperfecta, chondrodysplasia or Rett syndrome. However, over 50% of rare diseases appear during adulthood, such as Huntington diseases, Crohn disease, Charcot-Marie-Tooth disease, amyotrophic lateral sclerosis, Kaposi's sarcoma or thyroid cancer.

Rare diseases include many single gene disorders such as Huntington disease and Duchenne Muscular Dystrophy; many childhood and adult diseases, such as Guillain-Barré syndrome and Crohn’s disease; and some childhood cancers and infectious diseases. The economic impact of rare diseases is substantial not only for affected patients and their families, but for society as a whole.