Rett syndrome – Wikipedia

Rett syndrome (RTT) is a genetic disorder that typically becomes apparent after 6–18 months of age in females. Symptoms include impairments in language and coordination and repetitive movements. Those affected often have slower growth, difficulty walking, and a smaller head size. Complications of Rett syndrome can include seizures, scoliosis, and sleeping problems.

https://en.wikipedia.org/wiki/Rett_syndrome