Just a few decades ago, children born with significant congenital anomalies or genetic and metabolic diseases perished at an early age and very few survived into their teens and even less into adulthood. Congenital heart disease, major errors in metabolism, cancer, cystic fibrosis and many other major diseases were fatal. Because of that many physicians in adult primary care did not have the opportunity to see patients with these problems and thus unable to learn how to care for them. In this book, we have recruited highly qualified and experienced physicians to compile what is to the best of our knowledge, the first book dealing entirely with the issue of children's diseases in adults. Our goal is to provide a resource for all health care providers in order to help with caring for such adult patients. We believe that it will be valuable to all health care providers who provide care to adults with children's diseases. To our knowledge, there is no such resource available for practitioners which will make this book desirable.