Developmental delay in Rett syndrome: data from the natural history study

Area of Science:

• Neurodevelopmental disorders
• Genetics
• Pediatric neurology

Background:

• Rett syndrome (RTT) presents with seemingly normal early development, which may mask underlying issues.
• The Rett Syndrome Natural History Study (NHS) is the largest longitudinal assessment of RTT participants.
• This study examines developmental skill acquisition and phenotype-genotype correlations in RTT.

Purpose of the Study:

• To investigate the achievement of developmental skills in classic and atypical Rett syndrome.
• To analyze the relationship between genetic mutations and clinical presentation (phenotype-genotype).
• To provide data for planning and interpreting early intervention strategies for RTT.

Main Methods:

• Longitudinal assessment of developmental skills (gross/fine motor, communication) in 542 classic and 96 atypical RTT females over 7 years.
• Analysis of age at acquisition and loss of skills, and phenotype-genotype effects.
• Statistical comparisons using Fisher's Exact test, generalized estimating equations, and general linear models.

Main Results:

• Early developmental skills were acquired by many RTT individuals, but often at a later age than normal.
• More complex motor and communication skills were frequently delayed or absent.
• Individuals with specific mutations (R133C, R294X, R306C, 3' truncations) showed better developmental outcomes and milder clinical severity.

Conclusions:

• While many RTT individuals acquire early skills, significant deviations from normal development emerge, especially after 6 months of age.
• Greater skill acquisition is linked to specific mutations, indicating they confer milder developmental abnormalities.
• Findings support the use of these data for early intervention studies in RTT.