Arm Span and Its Relation to Height in a 2-to 17-Year-Old Reference Population and Heterozygous Carriers of ACAN Variants

Background/Objectives:In the clinical assessment of a short or tall child, estimating body disproportion is useful to assess the likelihood of a primary growth disorder, e.g., skeletal dysplasia. Our objectives were (1) to use data from the Maastricht study on healthy children (2-17 years) to calculate relative arm span (AS) for height (H) to serve as age references for clinical purposes; (2) to assess its age and sex dependency; and (3) to investigate relative AS adjustment for age and sex in individuals withACANhaploinsufficiency.Methods:The Maastricht study data (2,595 Caucasian children, 52% boys, 48% girls) were re-analysed to produce reference tables and graphs for age and sex of AS - H and AS/H. Published information on AS/H in Europeans was used as reference data for adults. Relative AS from 33 patients withACANhaploinsufficiency were plotted against reference data and expressed as standard deviation score (SDS) for age and sex.Results:Mean AS - H from 2 to 17 years increased from -1.2 to +1.5 cm in boys and from -4.8 to +1.6 cm in girls. Mean AS/H increased from 0.9848 to 1.0155 in boys and from 0.9468 to 1.0028 in girls. Mean AS/H in patients withACANhaploinsufficiency was approximately 1.0, 1.5 and 0.5 SDS in young children, adolescents and 20- to 50-year-olds, respectively, and normal thereafter.Conclusions:These reference charts can be used for 2- to 17-year-old children/adolescents. Carriers ofACANhaploinsufficiency have an elevated mean AS/H in childhood and adolescence and a slightly elevated ratio till 50 years.