Orphan drugs are those that are developed for the treatment of rare diseases and conditions. Tourette syndrome, Huntington's disease, muscular dystrophy, myoclonus, and ALS (Lou Gehrig's disease) are examples of rare diseases for which adequate drugs have not been developed, and thus these diseases are treated with orphan drugs. Orphan drugs are developed by pharmaceutical companies to meet a public health need, and their sales are very low when compared to standard drugs. Orphan diseases affect patient populations that account for 6-8 percent of the global population. Some orphan diseases, such as cystic fibrosis, infantile spinal muscular atrophy, familial adenomatous polyposis (FAP), and others, can cause symptoms at birth or in childhood.