Behavioral profiles in Rett syndrome: Data from the natural history study

Introduction: Rett syndrome (RTT) is a complex neurodevelopmental disorder with known behavioral abnormalities, both internalizing (e.g., anxiety, social withdrawal) and externalizing (e.g., aggression, self-abuse). However, a broad evaluation of behavioral abnormalities in a large cohort is lacking.

Objective: In this report, we describe profiles of internalizing and externalizing behaviors in individuals evaluated in the multi-center U.S. Rett Natural History Study.

Methods: Cross-sectional and longitudinal data were collected from 861 females with RTT and from 48 females who have MECP2 mutations without meeting criteria for RTT. Standard statistical methods including linear regression evaluated internalizing behavioral components from the Child Health Questionnaire (CHQ-PF50) and externalizing components from the Motor Behavioral Assessment (MBA).

Results: We found mildly to moderately severe internalizing behaviors in nearly all individuals with RTT, while externalizing behaviors were mild and uncommon. Internalizing behavior in RTT was comparable to groups with psychiatric disorders. Participants with mixed (internalizing and externalizing) behaviors were younger and less affected overall, but showed prominent self-injury and worsening internalizing behaviors over time.

Conclusions: This study revealed that internalizing behaviors are common at a clinically significant level in RTT. Understanding clinical features associated with behavioral profiles could guide treatment strategies.