Rett syndrome: a suggested staging system for describing impairment profile with increasing age towards adolescence.

A four-stage construction is presented for illustrating the characteristic clinical pattern and profile over the years in the average, 'classical' rett syndrome (RS) patient. The staging system was applied and evaluated in the 29 Swedish RS cases who now have passed age 13 (median 18). We also discuss the diagnostic pitfalls we have met and the conditions that need to be considered in the differential diagnosis.