Rare diseases affect 300 million patients around the world including 6 million people in Turkey.

Each year, Rare Disease Day is observed to raise awareness for rare diseases and improve access to treatment on the last day of February. Professor Ahmet Muzaffer Demir, the chairman of the Turkish Association of Dermatology, said the prevalence of a rare disease changes according to the region, country and population. There are 7,000 different types of rare diseases, and 80 percent of them are genetic diseases. Moreover, "Some contagious diseases are not inherited disorders but are included in the rare disease category," Demir said.

The pathology of many rare diseases is still unknown. "A disease or disorder is defined as rare in Europe when it affects less than 1 in 2000. In Europe and the United States, 60 million people are diagnosed with a rare disease. Based on U.S. National Health Institute statistics, rare diseases affect one-in-two patients during childhood. "Cross-cousin marriages are an important factor that raises the risk of developing a rare disease," Demir said.