A rare pervasive developmental disorder with a disease onset before the age of three and characterized by a dramatic loss of behavioral and developmental functioning after atleast two years of normal development. Manifestations of the disease include loss of speech, incontinence, communication and social interaction problems, stereotypical autistic behaviors and dementia. The disease is childhood disintegrative disorder (MONDO_0015681, a Monarch Disease Ontology term). Also known as: childhood disintegrative disease, dementia infantilis, disintegrative psychosis, heller syndrome, heller's syndrome, symbiotic psychosis.