Stages of the disease
Scientists generally describe four clinical stages of Rett Syndrome (RTT):
Stage I
Early-onset stagnation period
This stage begins between 6 and 18 months of age, before that, the development and growth is normal. There is a more or less sudden change in the interactive behaviour of the baby girl.
Stage II
Rapid developmental regression period
The transition to this stage occurs between ages 1 and 4 and may last for weeks or months. It’s characterized by rapid and specific regression of acquired abilities, such as the purposeful hand use and the ability to speak. Characteristic hand movements often begin during this stage.
Stage III
Pseudo-stationay stage
This stage starts when the regression stage is over, usually between ages 2 and 10 and can last for years. The typical hand stereotypies now become noticeable and constitute the hallmark of the disorder.
Stage IV
Late motor deterioration period
The last stage is marked by reduced mobility, muscle weakness and scoliosis. It starts when walking ceases and the girl becomes wheelchair-dependent, and can last for years or decades.