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

Abstract

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.

Figure 1.

(a) Clinical Severity Score vs age in females with classic and mild or severe atypical Rett Syndrome; (b) Motor Behavior Assessment vs age in females with classic and mild or severe atypical Rett Syndrome

Figure 2.

(a) Upper arm circumference vs age in females with classic and mild or severe atypical Rett Syndrome; (b) Upper arm muscle area vs age in females with classic and mild or severe atypical Rett Syndrome; (c) Triceps skinfold thickness vs age in females with classic and mild or severe atypical Rett Syndrome; (d) Lower leg skinfold thickness vs age in females with classic and mild or severe atypical Rett Syndrome

Figure 3.

(a) Biceps skinfold thickness vs age in females with classic and mild or severe atypical Rett Syndrome; (b) Subscapular skinfold thickness vs age in females with classic and mild or severe atypical Rett Syndrome; (c) Suprailiac skinfold thickness vs body mass index (BMI) in females with classic and mild or severe atypical Rett Syndrome

Figure 4.

(a) Thigh circumference vs age in females with classic and mild or severe atypical Rett Syndrome; (b) Thigh skinfold thickness vs age in females with classic and mild or severe atypical Rett Syndrome; (c) Lower leg circumference vs age in females with classic and mild or severe atypical Rett Syndrome; (d) Lower leg length vs age in females with classic and mild or severe atypical Rett Syndrome

Figure 5.

(a) Height vs age in females with classic and mild or severe atypical Rett Syndrome; (b) Weight vs age in females with classic and mild or severe atypical Rett Syndrome; (c) Body mass index (BMI) vs age in females with classic and mild or severe atypical Rett Syndrome; (d) Head circumference vs age in females with classic and mild or severe atypical Rett Syndrome

Figure 6.

Suprailiac skinfold thickness vs age in females with classic and mild or severe atypical Rett Syndrome