Turning the Unknown into Known: Data Mining Is Increasingly Used to Prospect for Rare-Disease Biology and Treatments.

Taken as a whole, rare diseases are not very rare. Even though a rare disease by definition is one that affects fewer than 200,000 Americans or fewer than one in 2,000 Europeans at any time, when rare diseases are considered together, they affect some 350 million people worldwide, or about 5% of the population (Figure 1). What is even more alarming is that 7,800 of the approximately 8,000 known rare diseases have no treatments available. It's not that rare diseases are harder to treat than more widespread illnesses. Rather, compared to more common disorders, rare diseases simply do not draw the same level of attention from granting agencies, pharmaceutical companies, medical professionals, and researchers, so they languish in the shadows.