223 Anderson tawil syndrome: expanding the phenotype and assessing cardiac risk

Anderson Tawil Syndrome (ATS) is a rare channelopathy traditionally characterised by periodic paralysis, cardiac arrhythmias and dysmorphic features. Mutations in the KCJN2 gene have been associated with ATS. Accurate and early diagnosis is important in facilitating treatment of episodic paralysis and preventing potentially life-threatening cardiac events. We aim to fully characterise the phenotype in a carefully stratified cohort including cognitive deficits and cardiac risk. 66 patients were identified with KCJN2 mutations. Comprehensive clinical information was available for 18 of these patients. Cardiac symptoms were prominent. Two thirds (11) had daily or very frequent palpitations. 27% (5) reported shortness of breath. Serious cardiac complications occurred in 4 patients (ICD insertion, left ventricular dysfunction/cardiomyopathy). 39% (7) reported pain which has previously not been appreciated as part of ATS. Interestingly, 4 patients had fasciculations. 4 patients had minimal decrement (<48%) on Long Exercise Tests (LET) despite having episodic weakness. Lower limb Muscle MRI was abnormal in 6 patients. Excess sleepiness was reported. Neuropsychometric testing suggests slowed processing speed. While dysmorphic features exist, these can be subtle. Short stature is not ubiquitous. Heterogeneity within families was commonly seen. The phenotypic spectrum of ATS is broader than currently appreciated, and data analysis is ongoing.