title: Rapsyn congenital myasthenic syndrome worsened by fluoxetine.
abstract: Fluoxetine is a selective serotonin reuptake inhibitor and long-lived open channel blocker of the acetylcholine receptor, often used in the treatment of slow-channel congenital myasthenic syndromes (CMS).
  
  
  
  We report a 42-year-old woman who had a history of episodic limb weakness that worsened after initiation of fluoxetine for treatment of depression. Genetic testing for CMS revealed a homozygous pathogenic mutation in the rapsyn (RAPSN) gene (p.Asn88Lys). Electrodiagnostic testing was performed before and 1 month after discontinuation of fluoxetine.
  
  
  
  The 2 Hz repetitive nerve stimulation of the fibular and spinal accessory nerves showed a baseline decrement of 36% and 14%, respectively. One month after discontinuing fluoxetine, the spinal accessory nerve decrement was no longer present, and the decrement in the fibular nerve was improved at 17%.
  
  
  
  This case demonstrates worsening of both clinical and electrophysiologic findings in a patient with CMS secondary to a RAPSN mutation treated with fluoxetine. Muscle Nerve 55: 131-135, 2017.
authors.affiliation: Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, Minnesota, 55905, USA.
authors.forename: Amy C
authors.initials: AC
authors.lastname: Visser
authors.affiliation: Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, Minnesota, 55905, USA.
authors.forename: Ruple S
authors.initials: RS
authors.lastname: Laughlin
authors.affiliation: Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, Minnesota, 55905, USA.
authors.forename: William J
authors.initials: WJ
authors.lastname: Litchy
authors.affiliation: Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, Minnesota, 55905, USA.
authors.forename: Eduardo E
authors.initials: EE
authors.lastname: Benarroch
authors.affiliation: Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, Minnesota, 55905, USA.
authors.forename: Margherita
authors.initials: M
authors.lastname: Milone
mesh_terms: D000328:Adult; D018687:Antidepressive Agents, Second-Generation / Q000009:adverse effects*; D005260:Female; D005473:Fluoxetine / Q000009:adverse effects*; D006801:Humans; D009124:Muscle Proteins / Q000235:genetics*; D009154:Mutation / Q000235:genetics*; D020294:Myasthenic Syndromes, Congenital / Q000139:chemically induced* / Q000235:genetics*; D010525:Peripheral Nerves / Q000187:drug effects / Q000503:physiopathology
chemical_list: D018687:Antidepressive Agents, Second-Generation; D009124:Muscle Proteins; C051609:peripheral membrane protein 43K; D005473:Fluoxetine
keywords: RAPSN, rapsyn gene; RNS; congenital myasthenic syndrome; fluoxetine; myasthenia; repetitive nerve stimulation