Researchers at the Miami Children’s Hospital and other centers in the US studied growth patterns among children with Rett syndrome compared to unaffected children. Growth charts for classic and atypical Rett were created from 9,749 observations of 816 female subjects. Mean growth in classic Rett decreased below that for the normative population at 1 month for head circumference, 6 months for weight, and 17 months for length. Mean BMI was unchanged. Pubertal increases in height and weight were absent in classic Rett patients. Classic Rett was associated with more growth failure than atypical Rett cases. In classic Rett, poor growth was associated with worse development, higher disease severity, and certain MECP2 mutations. 
COMMENT. More than 200 mutations identified in MECP2 are associated with growth velocity in Rett syndrome, and specific mutations are associated with developmental outcome. In a study of MECP2 mutations and clinical correlations in Greek children with Rett syndrome, mutations were detected in ~70% of classic and ~21% of variant Rett syndrome cases. MECP2-positive females had more problems in ambulation, muscle tone, tremor and ataxia, respiratory disturbances, head growth, hand use and stereotypies.