New phenotype and neonatal onset of sodium channel myotonia in a child with a novel mutation of SCN4A gene.
Myotonia is rare in newborns, and not well-known. Mutations of the skeletal muscle sodium channel gene SCN4A are associated with several neuromuscular disorders including sodium channel myotonias. We reported a 4-year-old female who presented with diffuse stiffness, bilateral clubfoot, hip dislocation, facial dysmorphisms and myotonia at birth. At 4 years of age the neurological examination showed characteristic "Hercules-like appearance" hyporeflexia, mild grip myotonia and bilateral pes cavus. The stiffness was worst at rest and in the early morning which improves with exercise. The clinical features, electromyography findings and diagnostic work-up of this patient and of child's mother were described. The clinical follow-up led us to the diagnosis of sodium channel myotonia with atypical neonatal onset. Mutation analysis in the patient and in child's mother revealed a novel heterozygous p.N1180I mutation in exon 19 of SCN4A gene. We recommend that in newborns with stiffness, peripheral contractures and myotonia, the sequence analysis of SCN4A gene should be performed.
Pediatric Neurology Unit, I.R.C.C.S. Arcispedale Santa Maria Nuova, 42123 Reggio Emilia, Italy. Electronic address: fusco.carlo@asmn.re.it.
Carlo
C
Fusco
Pediatric Neurology Unit, I.R.C.C.S. Arcispedale Santa Maria Nuova, 42123 Reggio Emilia, Italy.
Daniele
D
Frattini
Pediatric Neurology Unit, I.R.C.C.S. Arcispedale Santa Maria Nuova, 42123 Reggio Emilia, Italy.
Grazia Gabriella
GG
Salerno
Neurology Unit, I.R.C.C.S. Arcispedale Santa Maria Nuova, 42123 Reggio Emilia, Italy.
Elena
E
Canali
Neurology IV, Neuromuscular Diseases and Neuroimmunology Unit, I.R.C.C.S. Fondazione Istituto Neurologico "Carlo Besta", Via Celoria 11, 20133 Milano, Italy.
Pia
P
Bernasconi
Neurology IV, Neuromuscular Diseases and Neuroimmunology Unit, I.R.C.C.S. Fondazione Istituto Neurologico "Carlo Besta", Via Celoria 11, 20133 Milano, Italy.
Lorenzo
L
Maggi
D002675:Child, Preschool; D005260:Female; D006801:Humans; D018482:Muscle, Skeletal / Q000503:physiopathology; D009154:Mutation; D009224:Myotonia Congenita / Q000235:genetics* / Q000503:physiopathology; D062553:NAV1.4 Voltage-Gated Sodium Channel / Q000235:genetics*; D010641:Phenotype
D062553:NAV1.4 Voltage-Gated Sodium Channel; C106251:SCN4A protein, human
Arthrogryposis; Congenital myotonia; Electromyography; SCN4A