Rett syndrome (RTT) is an X-linked genetic disorder that causes severe neurological development disorder. In its classic form, it seems to affect almost exclusively females with an incidence of up to one in 10,000 females. Patients affected by Rett Syndrome can present a wide range of symptoms, in different combinations and of varying intensity, such as slowed growth of head circumference, abnormalities in walking and balance, loss of functional use of the hands often replaced by repetitive and stereotyped hand movements like hand washing, loss of communicative-relational skills including expressive language, epilepsy, breathing abnormalities, and osteo-muscular alterations. In light of the growing potential of clinical therapies, identification and early diagnosis are considered essential. Many disease modification strategies have been achieved through translational research studies and clinical trials that have allowed the recognition of the most effective therapeutic and clinical interventions to date. This study arises from the need to advance in the understanding of the pathogenesis of RTT through a multicentric collaboration in order to (a) identify early biomarkers of RTT (b) delve into the alterations of interconnectivity, crucial for understanding the loss of motor functions and language through systematic collection of anamnestic, genetic, and clinical-instrumental data. The aim is to provide a valuable contribution to the study of the clinical phenotype of Rett and the identification of early interventions.