The essential features of Childhood disintegrative Disorder is marked regression in multiple areas of functioning following a period of at least 2 years of apparently normal development, this must happen before age 10. Normal behaviour is shown in age appropriate verbal and non verbal communication, social relationships, play, and adaptive behaviour. After the first 2 years of life, the child has a clinically significant loss of previously acquired skills in at least 2 areas including; expressive or receptive language, social skills or adaptive behaviour, bowel or bladder control, play, or motor skills. Typically all of these acquired skills are lost. It appears likely that the resulting condition is caused by an insult on the developing central nervous system, although no precise mechanism has been identified. When a period of development has exceeded 5 years, it is particularly important to conducts thorough physical and neurological examination to assess for the presence of a general medical condition. In most cases the onset is between 3 and 4 years and may be gradual or abrupt. Some signs of the onset can include increased level of activity, irritability, and anxiety followed by a loss of speech and other skills. This disorder follows a continuous path and in the majority of cases, the duration is lifelong.
American Psychiatric Association: (2000) Diagnostic and Statistical Manual of Mental Disorders (4th Edition.). Text Revision. Washington, DC, American Psychiatric Association.