Home Page
References OMIM Gene GeneReviews HGMD HGNC
last update : 23-01-2018
Symbol DEL9Q34
Location 9q34.3
Name chromosome 9q subtelomere deletion syndrome
Other name(s)
  • Kleefstra Syndrome 1
  • 9q34.3 deletion syndrome
  • 9q subtelomere deletion syndrome
  • monosomy 9qter
  • Corresponding gene EHMT1
    Other symbol(s) 9qSTDS, KLEFS1
    Main clinical features
  • moderate to severe mental retardation
  • hypoplastic midface and supraorbital ridges, hypertelorism, synophrys, anteverted nares, cupid bow or tented upper lip, protruding tongue, high arched palate, neonatal teeth
  • microcephaly, hypotonia, obesity, speech impairment, behavioral problems
  • conotruncal heart defects, renal/urologic defects, genital defects in males, severe respiratory infections, epilepsy/febrile seizures, autistic-like features in childhood, and extreme apathy or catatonic-like features after puberty (PMID: 20945554))
  • Genetic determination chromosomal
    Function/system disorder mental retardation
    Type MCA/MR
    Gene product
    Name euchromatic histone methyltransferase 1, playing a role in chromatin remodeling
    Gene mutationChromosome rearrangementEffectComments
      deletion haploinsufficiency size from ~380kb to greater than 3Mb ; recurrent breakpoints identified at 0.8, 1.4, 2.2 and 2.8 Mb
      translocation haploinsufficiency t(X;9)(p11.23;q34.3) that disrupts EHMT1 gene
    various types     about 75p.100 of Kleefstra syndrome is caused by microdeletion of 9q34.3 and 25p.100 by intragenic EHMT1 mutation
    other epigenetic     In a cohort of KSS individuals without mutations in EHMT1 , de novo mutations in four genes, MBD5, MLL3, SMARCB1, and NR1I3, all of which encode epigenetic regulators, were identified.
    Genotype/Phenotype correlations five of six patients who had reached adulthood had developed severe psychiatric pathology, which may indicate that EHMT1 haploinsufficiency is associated with neurodegeneration in addition to neurodevelopmental defect