title: A de novo Mutation in the SCN4A Gene Causing Sodium Channel Myotonia.
abstract: We describe the case of a six year old boy with findings consistent with myotonia congenita: muscular hypertrophy, stiffness when commencing movements and typical warm-up signs. The most prominent symptom was myotonia of the eyelid muscles with apparent swelling around the eyes. Even though the pronounced warm-up phenomena in our patient suggested a chloride channel-associated myotonia congenita, the myotonia of his eyelid muscles indicated an involvement of sodium channels. Screening for mutations in the underlying CLCN1 gene was negative, however, in the SCN4A gene, we identified the missense mutation c.2108T>C; p.Leu703Pro for which there is strong evidence of pathogenicity because it arose de novo in the index patient.
authors.affiliation: Center for Hereditary Muscular Disorders, Department of Neurology, Oslo University Hospital, Oslo, Norway.
authors.forename: Kristin
authors.initials: K
authors.lastname: Ørstavik
authors.affiliation: Department of Clinical Neurosciences for Children, Oslo University Hospital, Oslo, Norway.
authors.forename: Sean Ciaran
authors.initials: SC
authors.lastname: Wallace
authors.affiliation: Center for Hereditary Muscular Disorders, Department of Neurology, Oslo University Hospital, Oslo, Norway.
authors.forename: Torberg
authors.initials: T
authors.lastname: Torbergsen
authors.affiliation: Medical Genetics Center, Munich, München, Germany.
authors.forename: Angela
authors.initials: A
authors.lastname: Abicht
authors.affiliation: Smestadbarnelegene, Oslo, Norway.
authors.forename: Svein
authors.initials: S
authors.lastname: Erik Tangsrud
authors.affiliation: Department of Neurology, Oslo University Hospital, Oslo, Norway.
authors.forename: Emilia
authors.initials: E
authors.lastname: Kerty
authors.affiliation: Center for Hereditary Muscular Disorders, Department of Neurology, Oslo University Hospital, Oslo, Norway.|Department of Clinical Neurosciences for Children, Oslo University Hospital, Oslo, Norway.
authors.forename: Magnhild
authors.initials: M
authors.lastname: Rasmussen
keywords: Myotonia; SCN4A; de novo mutation; eyelids