The essential feature of Childhood Disintegrative Disorder is a marked regression in multiple areas of functioning following a period of at least 2 years of apparently normal development (Criterion A).   Apparently normal development is reflected in age-appropriate verbal and nonverbal communication, social relationships, play, and adaptive behavior.   After the first 2 years of life (but before age 10 years), the child has a clinically significant loss of previously acquired skills in at least two of the following areas: expressive or receptive language, social skills or adaptive behavior, bowel or bladder control, play, or motor skills (Criterion B).   Most typically, acquired skills are lost in almost all areas.

      Individuals with this disorder exhibit the social and communicative deficits and behavioral features generally observed in Autistic Disorder.   There is qualitative impairment in social interaction (Criterion C1) and in communication (Criterion C2), and restricted, repetitive, and stereotyped patterns of behavior, interests, and activities (Criterion C3).   The disturbance is not better accounted for by another specific Pervasive Developmental Disorder or by Schizophrenia (Criterion D).   This condition has also been termed Heller's Syndrome, dementia infantilis, or disintegrative psychosis.

      Childhood Disintegrative Disorder is usually associated with severe mental retardation, which, if present, should be coded on Axis II.   Various nonspecific neurological symptoms or signs may be noted.   There seems to be an increased frequency of EEG abnormalities and seizure disorder.   Although it appears likely that the condition is the result of some insult to the developing central nervous system, no precise mechanism has been identified.   The condition is occasionally observed in association with a general medical condition (e.g.,metachromatic leukodystrophy, Schilder's disease) that might account for the developmental regression.   In most instances, however, extensive investigation does not reveal such a condition.   If a neurological or other general medical condition is associated with the disorder, it should be recorded on Axis III.   The laboratory findings will reflect any associated general medical conditions.

      Epidemiological data are limited, but Childhood Disintegrative Disorder appears to be very rare and much less common than Autistic Disorder, although the condition is likely underdiagnosed.   Although initial studies suggested an equal sex ratio, the most recent data suggest that the condition is more common among males.

      By definition, Childhood Disintegrative Disorder can only be diagnosed if the symptoms are preceded by at least 2 years of normal development and the onset is prior to age 10 years.   When the period of normal development has been quite prolonged (5 or more years), it is particularly important to conduct a thorough physical and neurological examination to assess for the presence of a general medical condition.   In most cases, the onset is between ages 3 and 4 years and may be insidious or abrupt.   Premonitory signs can include increased activity levels, irritability, and anxiety followed by a loss of speech and other skills.   During this time, the child may also lose interest in the environment.   Usually the loss of skills reaches a plateau, after which some limited improvement may occur, although improvement is rarely marked.   In other instances, especially when the disorder is associated with a neurological condition, the loss of skills is progressive.   This disorder follows a continuous course and in the majority of cases, the duration is lifelong.   The social, communicative, and behavioral difficulties remain relatively constant throughout life.

      Periods of regression may be observed in normal development, but these are neither as severe or as prolonged as in Childhood Disintegrative Disorder.   Childhood Disintegrative Disorder must be differentiated from other Pervasive Developmental Disorders.   For the differential diagnosis with Autistic Disorder, see autistic differential diagnosis.   For the differential diagnosis with Rett's Disorder, see Retts-Differential Diagnosis.   In contrast to Asperger's Disorder, Childhood Disintegrative Disorder is characterized by a clinically significant loss in previously acquired skills and a greater likelihood of Mental Retardation.   In Asperger's Disorder, there is no delay in language development and no marked loss of developmental skills.

      Childhood Disintegrative Disorder must be differentiated from a dementia with onset during infancy or childhood.   Dementia occurs as a consequence of the direct physiological effects of a general medical condition (e.g.,head trauma), whereas Childhood Disintegrative Disorder typically occurs in the absence of an associated general medical condition.