Rare diseases are frequently life-threatening, chronic illnesses. A rare disease is defined by the World Health Organization as a debilitating lifelong disease or disorder with a prevalence of 1 or less per 1000 people. Different countries, on the other hand, have their own definitions tailored to their individual needs and in the context of their population, health-care system, and resources. Medications developed specifically to treat rare disorders, known as "orphan drugs," are frequently left underdeveloped economically because of the minimal prospect for profit. Rare Diseases and Orphan Drugs demonstrates that studying rare diseases has led to much of what we currently know about common diseases. It posits that our rapid development in the field of rare diseases will lead to future advancements in the prevention, diagnosis, and treatment of common diseases. Rare disorders, on the other hand, are frequently caused by mutations in a single gene.