- A rare disease occurs infrequently in a population, but there is no universal definition. 3 elements to the definition as used in various countries are as follows:
- The total number of people having the disease
- Its prevalence
- Non-availability of treatment for the disorder
- A formal definition helps a nation to identify such diseases that require financial support for the discovery and development of drugs and biologics.This in turn helps in encouraging the product development improving the funding for basic and clinical research on rare diseases.
- The World Health Organization (W.H.O.) has suggested that a rare disease should be defined as one with frequency less than 6.5 – 10 per 10,000 people
- In USA, it is defined as any disease or condition that affects less than 200,000 persons.
- The affected numbers in Japan are 50,000