RS is classified as a developmental disease: it doesn’t cause the brain to degenerate. Rather, RS interferes with maturation of specific areas of the brain.

The areas of the brain disrupted in RS are the frontal, motor, and temporal cortex, brainstem, basal forebrain, basal ganglia, which control many basic functions, such as movement. They are also critical to the normal development of the cortex, or higher brain centre, in late infancy. RS, therefore, ravages centres that control both motion and emotion.

Barring illness or complications, survival into adulthood is expected. 

Because of unusual X inactivation patterns, some females with MECP2 mutations may be normal or have mild learning disability and will not be identified unless they transmit the mutation to a daughter who develops RS.