The dedication of this volume states:To the physicians and nurses who care for children in many different circumstances throughout the world and who, by their efforts and commitment, make the world a better place for children.I have used the Nelson Textbook of Pediatrics since its third edition. It remains a source of amazement to me, as I witness the evolution of the book and of the knowledge that dictates its scope. From the days when a textbook was written by 1 or 2 authors, we have progressed to the point where this would be impossible. Three editors preside over this volume; they are also counted among the 212 contributors that lend special expertise to the work, continuing the volume as one of the traditions of pediatrics.The tremendous and rapid explosion in the amount of knowledge in pediatrics made a revision of the total material and even of.