A rare disease/condition is defined as a condition that effects less than 200,000 people (in the USA). There are more than 7000 rare diseases and conditions currently identified, with more being discovered daily. There are more than 350 million people in the world living with a rare disease or condition, with about 30 million of them living in the United States (which is about 10% of the population). Sadly, since so few people are impacted by each individual condition, most rare diseases do not have a single FDA approved treatment and patients (and doctors) are left grasping at straws to find ways of managing the condition. Because there are no treatments, many patients are literally left to die. (Information from Global Genes RARE Disease Facts page)
These are some of the reasons we have World Rare Disease Day.