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Successful long-term therapy with flecainide in a family with paramyotonia congenita
  1. Chiara Terracciano1,
  2. Olimpia Farina2,
  3. Teresa Esposito3,4,
  4. Luca Lombardi2,
  5. Filomena Napolitano2,
  6. Paolo De Blasiis2,
  7. Gianluca Ciccone5,
  8. Vincenzo Todisco2,
  9. Francesco Tuccillo2,
  10. Sergio Bernardini1,
  11. Giuseppe Di Iorio2,
  12. Mariarosa Anna Beatrice Melone2,
  13. Simone Sampaolo2
  1. 1Department of Experimental Medicine and Surgery, Division of Clinical Biochemistry, University of Rome Tor Vergata, Roma, Lazio, Italy
  2. 2Department of Medicine, Surgery, Neurology, Metabolic and Aging Science, Reference Center for Neurological and Neuromuscular Rare Disease, Università degli Studi della Campania Luigi Vanvitelli, Napoli, Campania, Italy
  3. 3Molecular Genetics and Genomics Laboratory, Institute of Genetics and Biophysics, Adriano Buzzati Traverso, Italian National Research Council (CNR), Naples, Italy
  4. 4IRCCS, INM Neuromed, Pozzilli, Italy
  5. 5Division of Neurology, Local Health Unit of South Naples 3, Napoli, Campania, Italy
  1. Correspondence to Dr Chiara Terracciano, Department of Experimental Medicine and Surgery, Division of Clinical Biochemistry University of Rome Tor Vergata, 00133 Roma, Italy ; chiara.terracciano{at}uniroma2.it

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Introduction

Paramyotonia congenita (PC) is a neuromuscular disorder caused by point mutations of the sodium channel gene SCN4A that leads to gating defects in the sodium channel of the muscle membranes, thus resulting in a persistent sodium influx into the sarcoplasma. Classic PC phenotype is characterised by episodes of cold-induced stiffness, prominently in the facial and upper limb muscles, exacerbated by a sustained muscular activity (paramyotonia) and followed by a variable degree of weakness. Electromyography (EMG) at rest discloses myotonic bursts and reduced Compound Muscle Action Potential (CMAP) amplitudes, while short-term forearm exercise and cooling tests induce further decrease resulting in electrical silence in some patients. Muscle paralysis, after paramyotonic attacks, may last from a few dozen minutes to 24–48 hours, thus reducing considerable quality of life and autonomy in daily activities. Among voltage-gating sodium channel blockers, mexiletine is considered the drug of choice in PC and other sodium channel myopathies.1 However, mexiletine efficacy has been investigated only in a few heterogeneous small PC series during a month-lasting follow-up.

In experimental studies, flecainide, a class IC antiarrhythmic drug, appeared to be more effective than mexiletine to counteract SCN4A dysfunction.2 However, we lack long-term follow-up studies on flecainide efficiency in patients with PC with homogeneous pheno/genotype. The aim of this study was to assess the responsiveness to flecainide in a large family with classic PC phenotype by electrophysiological and quality of life evaluations.

Patients and methods

The Italian PC family pedigree includes 60 …

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