A quantitative three-dimensional assessment of abnormal variations in the facial soft-tissues of individuals with Down syndrome

OBJECTIVE: To supply quantitative information about the facial soft tissues of subjects with Down syndrome by using summary anthropometric measurements. DESIGN, SETTING, AND PATIENTS: The three-dimensional coordinates of soft tissue facial landmarks were obtained using a computerized digitizer in 28 subjects with Down syndrome (11 girls and women and 17 boys and men aged 12 to 45 years) and 429 healthy controls matched for sex, age, and ethnicity. From the landmarks, 18 facial dimensions were calculated. Data were compared with those collected in healthy individuals by computing z-scores. Two summary anthropometric measurements for quantifying craniofacial variations were assessed in both the subjects with Down syndrome and the reference subjects: the mean z-score (an index of overall facial size) and its standard deviation, craniofacial variability index (an index of facial harmony). RESULTS: In subjects with Down syndrome, facial size was smaller than in normal individuals, and in 17 subjects the mean z-score fell outside the normal interval (mean +/- 2 SD). Twenty subjects had a craniofacial variability index larger than the normal interval. CONCLUSIONS: The facial soft tissue structures of subjects with Down syndrome differed from those of normal controls of the same age, sex, and ethnic group: a reduced facial size was coupled with a global anomalous relationship between individual measurements. The two indices allowed discriminating more than 89% of subjects with Down syndrome when compared with normal subjects.