Rett’s disorder refers to a pervasive developmental disorder characterized by a deceleration of head growth in the early years, a loss of previously acquired purposeful hand skills with subsequent development of stereotyped hand movements, a loss of social engagement, poorly coordinated gait or trunk movements, severe impairments in expressive and receptive language development, and severe psychomotor retardation.
Other /More definition:
Rett’s disorder refers to progressive neurological developmental disorder featuring constant hand-wringing, mental retardation, and impaired motor skills.