More than 13,500 families from 24 regional genetics services across the UK and Ireland were recruited to the Deciphering Developmental Disorders (DDD) study. All the families had children with a severe developmental disorder, which was undiagnosed despite prior testing through their national health service and likely to be caused by a single genetic change. Combined with other high-tech methods, the team have so far been able to provide genetic diagnoses for around 5,500 children. The diagnoses were in over 800 different genes, including 60 new conditions previously discovered by the study.