Intractable diseases, literally derived from the Japanese word ‘nanbyo’, mainly refer to rare diseases that have resulted mostly from unidentifiable causes and/or lack of clearly established or curable treatments.

Currently, it is estimated that there are 5,000–7,000 distinct rare diseases worldwide, of which 80% have been identified as having genetic origins and 50% occurring in childhood and lasting for a lifetime. It is worth noting that most cancers including all cancers affecting children are within the scope of the concept of rare disease.

Rare diseases bring patients substantial physical suffering and psychological despair due to the lack of therapeutic hope and the absence of practical support for everyday life.

In addition, these kinds of diseases require a significant amount of labor for the patient's care, causing a heavy burden on other family members, both financially and mentally. Although each specific disease affects a limited number of patients because of its rarity, the total number of patients with rare diseases represents a striking proportion of the total population.

For example, in the European Union (EU) countries approximately 30 million people, which accounts for 6–8% of the total EU population, have various rare diseases. In the United States (US), it is estimated that 10% of people suffer from rare diseases.

These facts indicate that the situation of preventing and controlling rare diseases is grim in the world.