Early clinical signs in the Rett disorder.

This review of the period from birth until the end of regression in classic Rett syndrome (RS) is based on personal experience of more than 600 cases over 12 years including video material on 42 cases showing behaviour before regression. A period of undoubted developmental progress followed by loss of skill is apt to persuade the physician that a fresh toxic or infective insult has afflicted a normal child but close scrutiny of classic Rett syndrome cases indicates that the cognitive and motor problems of the disorder are detectable from birth, that a developmental ceiling limits progress and that the timing and nature of the regression event and subsequent behaviour of the child indicate inherently defective central receptive processing with a highly specific profile. A model illustrates how the characteristic disturbances may express incompetent higher control. The robust mid infancy level skills of the Rett child and woman deserve careful analysis and offer potential for therapy. Metabolic and immune sequelae may occur as the developmental defect becomes manifest and such cascade events demand careful evaluation and offer further opportunities for intervention.