title: [Clinical, electrophysiological and molecular study of 26 chilean patients with spinal muscular atrophy].
abstract: BACKGROUND
  Spinal Muscular Atrophy (SMA) is an autosomal recessive disorder affecting the anterior horn cells of the spinal cord resulting in muscle weakness and atrophy, linked to the homozygous disruption of the survival motor neuron 1 (SMN1) gene. It is the leading genetic cause of infant death. It has been classified into three types based on the severity of symptoms. Type I SMA is the most severe form with death within the first 2 years of life. Type II and III SMA patients show intermediate and mild forms of the disorder.
  
  
  OBJECTIVE
  To describe the clinical and electrophysiological findings of 26 Chilean patients with SMA with molecular confirmation.
  
  
  METHODS
  Retrospective multicenter analysis of patients with SMA assessed between 2003 and 2010. The diagnosis was suspected on clinical and electrophysiological criteria. Since 2006 molecular genetics confirmation was implemented in one of our centers.
  
  
  RESULTS
  Twenty-six patients between 2 months and 18 years of age at presentation were analyzed; 15 (58%) were males. SMA I, II and III clinical criteria were observed in 4 (15.4 %), 11 (42.3%) and 11 (42.3%)patients, respectively. All had proximal muscle weakness and atrophy. Electromyography showed features of acute denervation or re-innervation with normal motor and sensory nerve conduction. Nine patients required a muscle biopsy. The genetic confirmation of the disease by PCR technique followed by restriction fragment length polymorphism method disclosed the SMN1 gene deletion in all 26 cases. All patients died secondary to respiratory failure, between eight and 14 months of life.
  
  
  CONCLUSIONS
  An adequate clinical and molecular diagnosis of spinal muscular atrophy will help for a better management of these patients.
authors.affiliation: Unidad de Neurología, Departamento de Pediatría, Clínica Las Condes, Santiago, Chile. ccastiglioni@clc.c
authors.forename: Claudia
authors.initials: C
authors.lastname: Castiglioni
authors.forename: Jorge
authors.initials: J
authors.lastname: Levicán
authors.forename: Eliana
authors.initials: E
authors.lastname: Rodillo
authors.forename: María Angélica
authors.initials: MA
authors.lastname: Garmendia
authors.forename: Alejandra
authors.initials: A
authors.lastname: Díaz
authors.forename: Lorena
authors.initials: L
authors.lastname: Pizarro
authors.forename: Luis
authors.initials: L
authors.lastname: Contreras
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D004594:Electrophysiology; D005260:Female; D017353:Gene Deletion; D006801:Humans; D007223:Infant; D008297:Male; D009134:Muscular Atrophy, Spinal / Q000175:diagnosis* / Q000235:genetics / Q000503:physiopathology; D016133:Polymerase Chain Reaction; D012189:Retrospective Studies; D055533:Survival of Motor Neuron 1 Protein / Q000235:genetics
chemical_list: C526471:SMN1 protein, human; D055533:Survival of Motor Neuron 1 Protein