Question: What is (are) Rett Syndrome ?
Answer: Rett syndrome is a childhood neurodevelopmental disorder that affects females almost exclusively. The child generally appears to grow and develop normally, before symptoms begin. Loss of muscle tone is usually the first symptom. Other early symptoms may include a slowing of development, problems crawling or walking, and diminished eye contact. As the syndrome progresses, a child will lose purposeful use of her hands and the ability to speak. Compulsive hand movements such as wringing and washing follow the loss of functional use of the hands. The inability to perform motor functions is perhaps the most severely disabling feature of Rett syndrome, interfering with every body movement, including eye gaze and speech.
Source: NINDS

Question: what research (or clinical trials) is being done for Rett Syndrome ?
Answer: The National Institute of Neurological Disorders and Stroke (NINDS) and other institutes of the National Institutes of Health (NIH) conduct research related to Rett syndrome in laboratories at the NIH, and also support additional Rett syndrome research through grants to major medical institutions across the country. The discovery of the Rett syndrome gene in 1999 provides a basis for further genetic studies. Understanding the cause of this disorder is necessary for developing new therapies to manage specific symptoms, as well as for providing better methods of diagnosis.
Source: NINDS