Rett Syndrome is a neurological disorder that is known to almost exclusively affect girls. Rett Syndrome is estimated to affect 1 out of every 10,000-15,000 girls. Girls with Rett Syndrome seem to be developing at a normal rate, but then their growth and development slows. The disorder is characterized by distinctive hand movements, trouble walking, seizures, intellectual disability, and slowed head and brain growth. (NIH, 2009)