The immune system plays an unsuspected and surprising role in the progression of Rett syndrome, a severe neurological disorder affecting children, new research suggests. Rett syndrome is a neurodevelopmental disorder that is caused primarily by mutations in the gene encoding for MeCP2, an important epigenetic regulator. Children with the disorder appear to develop normally but begin to lose acquired cognitive and motor skills at 6 to 18 months of age as symptoms start to show. As they age, patients are unable to acquire verbal skills and suffer from lack of motor control.