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.
Keywords: Andersen-Tawil syndrome; anthropometry; facial feature, 3D; stereophotogrammetry.
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