Key result
De novo KCNJ2 mutation in Andersen-Tawil syndrome presents with unusual fixed myopathy from early childhood.
Case Report (n=1)
This case highlights an unusual presentation of Andersen-Tawil syndrome with early fixed myopathy in an Irish patient, expanding the known phenotypic spectrum of KCNJ2 mutations.
May prompt ATS consideration in neonatal seizures with myopathy; extends phenotypic spectrum but remains hypothesis-generating.
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.
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Lefter et al. (2014) conducted a case report in Andersen-Tawil syndrome (n=1). KCNJ2 mutation (R218W) was evaluated. A 19-year-old Irish man with Andersen-Tawil syndrome and a de novo KCNJ2 mutation presented with an unusual fixed myopathy from early childhood.
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