"Approximately 25–30 million individuals in the United States are living with a rare disease. ... Many children with rare diseases remain undiagnosed throughout life, leading to excess medical care, expensive diagnostic odysseys, and frustration for patients and their families. ... Advances in genomic technology have allowed for more comprehensive genetic analyses of patients with rare diseases. In an effort to better characterize patients with rare and undiagnosed diseases, the National Institutes of Health launched a single-site project, the Undiagnosed Diseases Program, to improve our understanding of the etiology of these disorders. Following initial success, the program expanded to encompass additional clinical and research institutions, thus establishing the Undiagnosed Diseases Network. ... The UDN is a network of investigators across 13 institutions designated to serve public need by bringing expertise in clinical diagnostics, translational research, and multi-omics technologies to solve medical mysteries ..."