The doctors involved in the Undiagnosed Diseases Network (UDN) are real-life House M.D.s. We’re using genome sequencing along with a network of specialists from numerous medical disciplines at seven clinical sites around the country to diagnose the most challenging and rare genetic diseases. But rare genetic diseases aren’t so rare. The National Organization for Rare Disorders (NORD), as well as the Rare Diseases Act of 1983, defines a rare disease as one that affects fewer than 200,000 people in the United States. And even despite the impressive state of medical technology today, the causes of many rare genetic diseases remain mysteries. Since accepting its first patient in 2015, the UDN – an NIH-funded program – has been trying to find the causes and treatments for patients with unknown disorders and to help provide answers for families that have nowhere else to turn. The UDN is an expansion of an Undiagnosed Diseases Program initiated in 2008 within the Intramural Research Program of the National Human Genome Research Institute (NHGRI). This week at NIH and around the world, we celebrated Rare Disease Day. To help raise awareness in the science community and share info about rare diseases and their impact on patients’ lives, we’re here today to answer your questions about rare diseases, how the UDN is using genomic techniques to find cures, or just how to find support if you or a loved one is suffering from a rare, undiagnosed condition. Today’s AMA brings together us – two UDN investigators at the NIH Clinical Center – along with Chad Smith, the father of a young boy with a rare, unidentified condition whom we evaluated at the Clinical Center in June 2016. A bit more about us. We are: Dr. William Gahl: Clinical Director, and Head of the Undiagnosed Diseases Program (UDP) at NHGRI, one of seven clinical sites within the UDN. Dr. Cyndi Tifft: Deputy Clinical Director, and Head of the Pediatric portion of the UDP at NHGRI. Mr. Chad Smith (aka “Chad the Dad”): Father of Blake, an 8-year old undiagnosed child who is currently being researched by the UDN. We will be answering your questions at 1 p.m. ET – Ask Us Anything! Update: We’re signing off for now, but thanks to the Reddit community for such thoughtful and engaging questions! We had a blast and hope to do it again sometime to share more stories from the Undiagnosed Diseases Network. (More info here: https://undiagnosed.hms.harvard.edu/)