Interfamilial phenotypic heterogeneity in SMARD1

Neuromuscul Disord. 2009 Mar;19(3):193-5. doi: 10.1016/j.nmd.2008.11.013. Epub 2009 Jan 20.


Spinal muscular atrophy with respiratory distress (SMARD1: mu-binding protein 2 gene mutation) is characterised by low birth weight, progressive distal limb weakness, diaphragmatic paralysis and subsequent respiratory failure manifesting before 13 months of age. Our case report illustrates marked phenotype variability in two siblings with an identical genetic mutation of SMARD1, one of whom died of fulminant respiratory failure aged 6 months, whereas the other shows limb weakness but, only mild sleep hypoventilation aged 12 years. This suggests other compensatory mechanisms may play a role in modifying SMARD1; broadening our perception of phenotype. Therefore, SMARD1 phenotype should be considered in cases of atypical spinal muscular atrophy even in the absence of overt diaphragmatic weakness.

Publication types

  • Case Reports

MeSH terms

  • Adolescent
  • DNA Mutational Analysis
  • DNA-Binding Proteins / genetics*
  • Disease Progression
  • Fatal Outcome
  • Female
  • Genetic Markers / genetics
  • Genetic Predisposition to Disease / genetics*
  • Genotype
  • Humans
  • Infant
  • Muscle Weakness / genetics
  • Muscular Atrophy, Spinal / genetics*
  • Mutation / genetics*
  • Phenotype
  • Respiratory Insufficiency / genetics*
  • Respiratory Paralysis / genetics
  • Siblings
  • Transcription Factors / genetics*


  • DNA-Binding Proteins
  • Genetic Markers
  • IGHMBP2 protein, human
  • Transcription Factors