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References OMIM Gene GeneReviews HGMD HGNC
last update : 11-05-2018
Symbol SBMA
Location Xq12
HGNC id 10543
Name spinal and bulbar muscular atrophy
Other name(s)
  • Kennedy disease
  • Kennedy spinal and bulbar muscular atrophy
  • Corresponding gene AR
    Other symbol(s) KD, SMAX1
    Main clinical features
  • adult-onset motoneuron disease caused by a CAG-repeat expansion in the androgen receptor
  • muscle weakness and atrophy, fasciculations, dysphagia and dysarthia
  • associated with gynecomastia and testicular atrophy and mild androgen insensitivity maybe due to poor and weak interaction of RAN (ARA24) with longer poly-Q repeat (see RAN)
  • Genetic determination sex linked
    Function/system disorder neuromuscular
    Type disease
    Gene product
    Name androgen receptor (AR)
    Gene mutationChromosome rearrangementEffectComments
    repeat expansion   other triplet (CAG) repeat amplification (polyglutamine stretch, 38-62) accumulating in both cytoplasmic and nuclear aggregates with a prominent somatic mosaicism observed in the cardiac and skeletal muscle
    Remark(s) mitochondrial dysfunction in SBMA cell and animal models, either through indirect effects on the transcription of nuclear-encoded mitochondrial genes or through direct effects of the mutant protein on mitochondria or both (Ranganathan 2009)
    Genotype/Phenotype correlations
  • longer CAG repeat is more closely linked to the motor-dominant phenotype and a shorter CAG repeat is more closely linked to the sensory-dominant phenotype, and CAG repeat size differentially correlates with motor- and sensory-dominant phenotypes (Suzuki 2008)