Anthropometric Measures Correspond with Functional Motor Outcomes in Females with Rett Syndrome.

OBJECTIVE: To characterize growth and anthropometric measurements in females with Rett syndrome and compare these measurements with functional outcomes. STUDY DESIGN: We obtained longitudinal growth and anthropometric measurements from 1154 females with classic and atypical Rett syndrome seen between 2006 and 2019 in the US Natural History Study. We calculated the Clinical Severity Score, Motor Behavior Assessment score, and arm and leg muscle areas and recorded the functional assessments of arm and hand use and ambulation. We compared growth and anthropometric variables from females with Rett syndrome in regard to normative data. We analyzed Clinical Severity Score, Motor Behavior Assessment, and anthropometric measurements in regard to functional assessments. RESULTS: Growth and anthropometric measurements were significantly lower in females with classic and severe atypical Rett syndrome compared with those classified as mild atypical Rett syndrome and deviated from normative patterns among all 3 groups. Suprailiac skinfold measurements correlated with body mass index measurements in each group. Lower leg muscle area measurements were significantly greater among females in all 3 Rett syndrome groups who ambulated independently compared with those who did not. In females with classic Rett syndrome, arm, thigh, and lower leg muscle area measurements increased significantly over time and were significantly greater among those who had purposeful arm and hand use and independent ambulation compared with those who did not. CONCLUSIONS: The pattern of growth and anthropometric measures in females with Rett syndrome differs from normative data and demonstrates clear differences between classic and mild or severe atypical Rett syndrome. Anthropometric measures correspond with functional outcomes and could provide markers supporting efficacy outcomes in clinical trials.

Longevity in Rett syndrome: analysis of the North American Database.

OBJECTIVE: To determine longevity in Rett syndrome (RTT) from a large cohort. STUDY DESIGN: The North American RTT Database allows the examination of longevity in a large cohort of individuals with RTT from the United States and Canada. This database contains information on 1928 individuals, 85.5% with typical RTT, 13.4% with atypical RTT, and 1.1% with a mutation in the methyl-CpG-binding protein 2 gene (MECP2) but not RTT. Kaplan-Meier analyses were performed to assess longevity. RESULTS: Earlier decennial cohorts exhibited better survival than recent cohorts, with most participants surviving into middle age. Comparing overall survival in persons with typical RTT and atypical RTT revealed greater mortality in typical RTT across the observed lifespan (P < .0001). Comparing survival in persons with RTT and identified MECP2 mutations and persons with unknown MECP2 status demonstrated greater mortality in the latter group (P < .0001, log-rank test). CONCLUSIONS: This analysis provides strong evidence for significant longevity in RTT and indicates the need for careful planning for long-term care of these women. The disproportionately greater survival seen in earlier time periods and in persons with atypical RTT may be attributed to more severely affected individuals dying before diagnosis in the former and to greater numbers with milder variants (ie, preserved speech and delayed onset) in the latter.