Pervasive developmental disorders (PDDs) is a term that refers to a set of conditions involving some form of delay in basic skill development. Most commonly, it affects how a patient communicates, socializes with other people, and uses their imagination. PDDs are generally diagnosed in young children at about three years of age. At this stage of development, affected kids often become confused and have a difficult time comprehending their world. Though researchers are looking for answers, it is not yet known what exactly causes these conditions.
PDDs typically begin much earlier, but symptoms are not often visible until the toddler stage, when it becomes noticeable to parents that their child is developing differently from his peers.