The government is expanding its "mystery disease" program, funding a network at six universities around the country to help diagnose patients with diseases so rare they've been told they're undiagnosable. The National Institutes of Health has evaluated hundreds of these cold-case patients in its campus research hospital as part of a pilot program since 2008. Demand is so great, there's a waiting list. So on Tuesday, the agency announced the NIH Undiagnosed Diseases Network, a four-year, $43 million initiative to bring more doctor-detectives on board in the quest to at least put a name to more patients' puzzling symptoms, and eventually find treatments.