A rare disease, often known as an orphan disease, is a medical disease that only affects a small percentage of the population. A pharmacological agent developed specifically to treat an orphan disease is known as an orphan drug. The journey from the discovery of a new drug to its commercialization is lengthy (10 years on average), costly (tens of millions of euros), and fraught with risk (among ten molecules tested, only one may have a therapeutic effect). The development of a drug to treat a rare condition does not allow for the recovery of the money spent on research. Over the previous two decades, the percentage of new medicines approved for orphan drugs has risen considerably. Approximately 500 orphan designated medications have been approved for the treatment of a variety of oncological, metabolic, hematologic, immunologic, infectious, and neurological disorders. Patients with rare diseases must be kept up to date on scientific and treatment developments.