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last update : 13-11-2013
Symbol ISSX
Location Xp22.13
Name infantile spasms syndrome with hypsarrhythmia
Other name(s) West syndrome, infantile encephalopathy with seizures
Corresponding gene ARX , CDKL5
Other symbol(s) XMESID
Main clinical features
  • early onset seizures before the age of 3 months, including myoclonic epilepsy with spasticity and mental retardation, Rett-like lacking early normall period
  • significant cause of infantile spasms and early epileptic seizures in female patients, and of a later intractable seizure disorder, irrespective of whether they have suspected Rett syndrome
  • Genetic determination sex linked
    Related entries RTTA
    Function/system disorder neurology
    Type disease
    Gene product
    Name . aristaless related homeobox . cyclin-dependent kinase-like 5
    Gene mutationChromosome rearrangementEffectComments
    frameshift   truncated protein resulting in exon skipping in CDKL5
    missense   abnormal protein/loss of function disruption of DNA binding or protein stability
    missense     within the homeodomain of ARX
      translocation   t(X;A) with CDKL5 disruption
    various types     mostly truncating mutations
    Remark(s) expansion of the first alanine tract of ARX (binding of these expanded polyalanine tract mutant ARX proteins to IPO13 may be less efficient than that of the normal ARX protein and may lead to compromised nuclear import, contributing in part to the molecular pathogenesis of these disorders)
  • expansion of pA2 of ARX beyond 20 residues with dup27 bp mutation expands pA2 from 12A to 21A and resulting phenotype for hemizygous c.430_456dup(27 bp) males is infantile spasms with a consistent early age of onset (2 months) and death early in life (Reish 2009)