title: Phenotypic variation of Val1589Met mutation in a four-generation Chinese pedigree with mild paramyotonia congenitia: case report.
abstract: Four generations of a Chinese family with a mild form of paramyotonia congenital was characterized in phenotype and genotype. For each member, clinical history, physical examination, laboratory tests, electrophysiological and gene analyses were recorded and carried out. A potassium loading, exercise and cold provocation were further tested to diagnose the clinical differentiation. All members shared the characteristics of mild muscle cramp and stiffness induced by exercise or exposed to cold. The symptoms were relieved after rest and warming. A Val1589Met mutation at exon 24 of the SCN4A gene appears in affected subjects, while healthy members had a point mutation at position 1513 at exon 24 of the SCN4A gene. The mild phenotype of the paramyotonia congenital in the family had a Val1589Met mutation in the SCN4A gene. Various phenotypes can exist among different families, indicating that family, individual, genetic or environmental factors influence symptoms.
authors.affiliation: Department of Neurology, People's Hospital of Zhengzhou University Zhengzhou, China.
authors.forename: Changshui
authors.initials: C
authors.lastname: Xu
authors.affiliation: Department of Neurology, People's Hospital of Zhengzhou University Zhengzhou, China.
authors.forename: Junjia
authors.initials: J
authors.lastname: Qi
authors.affiliation: Department of Neurology, People's Hospital of Zhengzhou University Zhengzhou, China.
authors.forename: Yingying
authors.initials: Y
authors.lastname: Shi
authors.affiliation: Department of Neurology, People's Hospital of Zhengzhou University Zhengzhou, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Feng
authors.affiliation: Department of Neurology, People's Hospital of Zhengzhou University Zhengzhou, China.
authors.forename: Weizhou
authors.initials: W
authors.lastname: Zang
authors.affiliation: Department of Neurology, People's Hospital of Zhengzhou University Zhengzhou, China.
authors.forename: Jiewen
authors.initials: J
authors.lastname: Zhang
mesh_terms: D000328:Adult; D044466:Asian People; D004252:DNA Mutational Analysis; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D009154:Mutation; D020967:Myotonic Disorders / Q000235:genetics*; D062553:NAV1.4 Voltage-Gated Sodium Channel / Q000235:genetics*; D010375:Pedigree; D010641:Phenotype; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D062553:NAV1.4 Voltage-Gated Sodium Channel; C106251:SCN4A protein, human
keywords: Paramyotonia congenita; SCN4A; Val1589Met; myotonia; phenotype