Rett syndrome: report of a new pathogenic variant and review of the literature regarding two clinical cases

Background: Rett syndrome is an X-linked neurodevelopmental disorder with an estimated frequency of 1/10,000 live births caused by hetereozygous pathogenic variants in the MECP2 gene, whose protein participates in the development and differentiation of the central nervous system. This study aimed to describe two cases with Rett syndrome diagnosis, one of them with a new variant of the MECP2 gene. Case reports: We first describe the case of a 5-year-old female with microcephaly and neurodevelopmental regression starting at 3 years old, clinically corresponding to stage III Rett syndrome. Sequencing of the MECP2 gene identified a heterozygous likely pathogenic variant [c.606delC (p.Thr203Argfs*7)] not reported previously. The second case is a 17-year-old female, referred due to severe intellectual disability, clinically found on stage IV. MECP2 sequencing was performed identifying a pathogenic variant previously described [c.880C> T (p.Arg294 *)]. Conclusions: Rett syndrome clinical diagnosis was carried out based on established criteria. MECP2 sequencing confirmed the diagnosis. For neurodevelopmental disorders approach, it is essential to know the phenotype of Rett syndrome and select the molecular tool for the diagnosis. Patients with Rett syndrome require interdisciplinary follow-up for reducing the impact of complications.