The UDNF works closely with the UDN, a research study backed by the National Institutes of Health (NIH) that brings together clinical and research experts from across the United States to evaluate undiagnosed patients. The UDN consists of 12 clinical sites, two model organisms screening centers (MOSCs), a coordinating center, a sequencing core, a metabolomics core, and central biorepository. Patients can apply directly online using the UDN’s application gateway.