title: Andersen-Tawil syndrome with early fixed myopathy.
abstract: Andersen-Tawil syndrome (ATS) is a rare autosomal dominant potassium channelopathy characterized by a triad of periodic paralysis, ventricular arrhythmias, and distinctive dysmorphic abnormalities. We present a 19-year-old man with characteristic skeletal dysmorphic features of ATS, early nonfluctuating proximal lower limb weakness from childhood, and neonatal focal seizures. He later developed fluctuating weakness in addition to a fixed proximal myopathy. A 12-lead electrocardiogram showed prominent "U" waves, and McManis protocol prolonged exercise test showed an unusually early decline in the compound motor action potential amplitude by 51%. Genetic testing revealed a de novo heterozygous mutation (R218W) in KCNJ2 associated with ATS. This is the first reported case of ATS in an Irish population with an unusual fixed myopathy from early childhood.
authors.affiliation: *Department of Neurology, Cork University Hospital, Cork, Ireland; †Department of Neurology, Beaumont Hospital, Dublin, Ireland; ‡Mater Private Hospital, Dublin, Ireland; §Department of Neurology, Children's University Hospital, Dublin, Ireland; ¶Department of Neurology, Belfast City Hospital, Northern Ireland, United Kingdom; and ‖Department of Pathology, University College Cork, Cork, Ireland.
authors.forename: Stela
authors.initials: S
authors.lastname: Lefter
authors.forename: Orla
authors.initials: O
authors.lastname: Hardiman
authors.forename: Donal
authors.initials: D
authors.lastname: Costigan
authors.forename: Bryan
authors.initials: B
authors.lastname: Lynch
authors.forename: John
authors.initials: J
authors.lastname: McConville
authors.forename: Collette K
authors.initials: CK
authors.lastname: Hand
authors.forename: Aisling M
authors.initials: AM
authors.lastname: Ryan
mesh_terms: D050030:Andersen Syndrome / Q000150:complications* / Q000235:genetics / Q000473:pathology; D006801:Humans; D008297:Male; D009135:Muscular Diseases / Q000235:genetics*; D009154:Mutation; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics; D055815:Young Adult
chemical_list: C489457:KCNJ2 protein, human; D024661:Potassium Channels, Inwardly Rectifying