For a study, researchers sought to define and compare growth and anthropometric parameters in girls with Rett syndrome with functional results. They acquired longitudinal development and anthropometric measures from 1,154 females with classic and atypical Rett syndrome seen in the US Natural History Study between 2006 and 2019. The Clinical Severity Score, Motor Behavior Assessment score, and arm and leg muscle areas were computed, and functional evaluations of arm and hand usage and ambulation were recorded. In comparison to normal data, they compared growth and anthropometric factors in girls with Rett syndrome. Regarding functional evaluations, they looked at the Clinical Severity Score, Motor Behavior Assessment, and anthropometric data. 

Females with classic and severe atypical Rett syndrome had considerably lower growth and anthropometric measures than those with moderate atypical Rett syndrome, and all three groups varied from normative trends. In each group, suprailiac skinfold measures were associated with body mass index values. Females in all three Rett syndrome groups who ambulated independently had considerably larger lower leg muscle area measures than those who did not. Arm, thigh, and lower leg muscular area measures grew considerably over time in girls with typical Rett syndrome. It was significantly higher in those who exhibited intentional arm and hand usage and independent ambulation than in those who did not.

The growth pattern and anthropometric parameters in females with Rett syndrome differed from normative data, demonstrating obvious distinctions between classic and moderate or severe atypical Rett syndrome. In addition, anthropometric metrics correlated with functional results and may be used to support efficacy outcomes in therapeutic studies.