Distinctive facial features in Andersen–Tawil syndrome: A three‐dimensional stereophotogrammetric analysis

Andersen-Tawil syndrome (ATS) is a rare potassium channelopathy causing periodic paralysis, cardiac arrhythmias, and dysmorphic features. A detailed analysis of the face could facilitate diagnosis of ATS, as approximately 30% of patients do not show variants in KCNJ2 gene, and diagnosis is established by clinical findings. We aimed to characterize the face in ATS through a quantitative approach, as facial anomalies may be unnoticed on visual inspection. Facial images of 12 subjects with genetically confirmed ATS (six males, six females, age 5-67 years) were acquired through stereophotogrammetry. Using 38 soft-tissue landmarks, linear distances, angles, and ratios were calculated and expressed as z-score values, with reference to 477 healthy subjects matched for sex and age. All patients showed decreased lower facial height with shortening of philtrum (mean z-score +/- SD: -1.5 +/- 0.9), smaller mid and lower facial depths (-1.9 +/- 0.7; -2.3 +/- 0.9), short palpebral fissures (right -1.2 +/- 0.4; left -1.6 +/- 0.6), smaller mandibular ramus length (-2.1 +/- 0.4), and increased nasal width/length ratio (1.4 +/- 0.5) with smaller nostril axis length (right -1.8 +/- 0.8, left -1.6 +/- 0.7). Hypertelorism and low-set ears were detected in two-thirds of patients. The study quantified facial dysmorphysm in ATS, extending information about known features, and detecting unrecorded philtrum and nostril characteristics, which may be distinctive traits of the disorder.