Researchers at the University of Iowa and Washington University, St Louis, MO, studied the effect of the mutant Huntington gene (mHTT) on measures of growth in children at risk for Huntington disease (HD). Measurements of growth (height, weight, body mass index [BMI], and head circumference) in 20 at risk gene-expanded children, aged 7-18 years, with no symptoms were compared with measurements in 14 gene-nonexpanded children and 138 age-matched healthy controls. Children with a CAG repeat length =/+ 39 were designated as gene-expanded. At risk gene-expanded children had significantly lower measures of head circumference, weight, and BMI. Head circumference was abnormally low even after correcting for height, suggesting a specific defect in brain growth, rather than a global growth abnormality. mHTT may play a role in atypical somatic, and particularly, brain development. 
COMMENT. Children tested as HD gene expanded were an estimated >3 decades from onset of the disease. Constant caloric burn due to chorea is a possible cause of weight loss in HD patients but not in preHD children. A primary abnormality in mitochondrial function and metabolic rate is more likely.