People with MECP2 mutation-positive Rett disorder who converse.

Area of Science:

• Neurology
• Genetics
• Developmental Biology

Background:

• Rett syndrome is a rare genetic neurodevelopmental disorder.
• A small subset of individuals with Rett syndrome (mutation-positive) retain useful speech after regression.
• Understanding the characteristics of this subgroup is crucial for accurate diagnosis and management.

Purpose of the Study:

• To investigate the physical, mental, and genetic traits of individuals with Rett syndrome who have useful speech post-regression.
• To gain insights into the lived experiences of this distinct patient group.
• To identify potential diagnostic markers and understand the genetic underpinnings of milder Rett syndrome phenotypes.

Main Methods:

• A cohort of 13 individuals (aged 10+) with Rett syndrome and conversational ability, confirmed MECP2 mutation, were studied.
• Clinical and molecular data were collected and analyzed.
• Comparison was made with an age-matched control group (n=110) lacking conversational ability but possessing a pathogenic MECP2 mutation.

Main Results:

• The study group exhibited significantly milder disease severity, fewer feeding difficulties, better health scores, and less epilepsy compared to controls.
• Six individuals in the study group did not experience regression, and age at onset of regression differed significantly.
• Specific mutations (C-terminal deletions, R133C) were more frequent in the study group, suggesting a genetic association with milder phenotypes and favorable X-inactivation skewing.

Conclusions:

• Individuals with Rett syndrome and speech are often not classic cases, and features like speech, good head growth, and lack of regression can lead to missed diagnoses.
• The R133C mutation and C-terminal deletions are strongly associated with this milder form of Rett syndrome.
• Despite milder symptoms, cognitive and executive function remain restricted in most individuals.