Symptom Onset in Classic Rett Syndrome: Analysis of Initial Clinical Severity Scale Entries

Area of Science:

• Neurology
• Genetics
• Pediatrics

Background:

• Rett Syndrome (RTT) is a rare neurodevelopmental disorder.
• The Clinical Severity Scale (CSS) was developed in 2000 to assess RTT characteristics.

Purpose of the Study:

• To evaluate the clinical features of individuals with classic RTT at enrollment in the NIH Natural History study using the CSS.
• To assess the utility of the CSS in capturing core RTT clinical criteria.

Main Methods:

• Analysis of the CSS data from 1258 individuals with classic RTT.
• Examination of historical items (age at regression, hand stereotypies, head growth) and ten clinical features at enrollment.

Main Results:

• Key developmental milestones like regression, hand stereotypies, and head growth were analyzed.
• Delayed regression (after 12 months) and onset of hand stereotypies (after 18 months) were observed.
• Reduced hand use, ambulation, and communication skills were prevalent in most participants.

Conclusions:

• The CSS accurately reflects core clinical criteria for classic RTT and aligns with caregiver concerns.
• The CSS is valuable for analyzing clinical outcomes, stratifying participants for clinical trials, and understanding genotype-phenotype correlations (e.g., with MECP2 variants).
• Age-specific CSS features will guide future RTT research and clinical trial design, particularly for younger populations.