Genotype-Phenotype Relationships in Language Processes in Rett Syndrome

Rett syndrome (RTT) is a neurodevelopmental disorder mainly caused by mutations in the MECP2 gene affecting around 1 in 10,000 female births. Mutations in the MECP2 gene have been associated with the onset of RTT. Clinical manifestations include severe linguistic and motor impairments that are the core of phenotype symptoms. Some patients show a moderate level of conservation of linguistic functions while others lose the use of functional verbal communication. The objectives of the present chapter are to study in depth the latest theoretical approaches to the link between linguistic processes and the specific RTT genotype. This chapter begins with a theoretical overview on cognitive alterations and then focuses on linguistic specific impairments characterized by the loss of articulation or the production of few functional sounds. A restricted sample shows the presence of verbal speech (Preserved Speech Variant). Renieri et al. (2009) proposed the term ‘‘Zappella variant’’ rather than ‘‘preserved speech variant’’ to describe milder forms of RTT, because other aspects, besides speech, are involved. The second part proposes a preliminary research which analyses the correlation between linguistic phenotype and specific genotype.