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GENATLAS PHENOTYPE
last update : 23-05-2012
Symbol DUPXQ28
Location Xq28
Name chromosome Xq28 (MECP2) duplication
Other name(s) MECP2 duplication, Xq28 functional disomy
Corresponding gene MECP2 , SLC6A8 , L1CAM , FLNA , GDI1
Other symbol(s) DUPXQD
Main clinical features
  • facial dysmorphic features with a wide face, a small mouth and a narrow "pinched" appearance of the nose, with a translucent quality of the skin and prominent veins
  • severe mental retardation, absent or limited speech, severe hypotonia at birth followed in most cases by progressive lower-limb spasticity, severe feeding problems and proneness to infections
  • gastro-intestinal and bowel symptoms in some patients (intestinal pseudo-obstruction)
  • ataxia or ataxic gait, and cerebral atrophy in some cases
    • Genetic determination chromosomal
    sex linked
    Prevalence . in 1 percent of unexplained XLMR and in 2 percent of male patients with severe encephalopathy
    Related entries RTTM (MECP2 associated disorders in males)
    Function/system disorder multisystem/generalized
    mental retardation
    neurology
    Type MCA/MR
    Mechanism(s)
    Gene mutationChromosome rearrangementEffectComments
      translocation over-expression unbalanced Y; X translocation with Xq terminal duplication
      translocation over-expression cryptic unbalanced X ; autosome translocation, de novo
      inversion over-expression unbalanced inversion resulting in duplication Xq and deletion Xp, sometimes inherited from a phenotypically normal mother
      duplication over-expression interstitial, of variable size, including MECP2,IRAK1 and possibly other genes L1CAM, FLNA, GDI1
      duplication   of 0.3 MB including FLNA and GDI1 but not MECP2 in 4 unrelated MR families (MIM 300815)and different clinical features (PMID: 20082459)
      duplication   from ∼0.08 to 14.13 Mb PMID: 22581587
    Remark(s) MECP2 is the most important dosage-sensitive gene responsible for neurologic impairment in these patients; FLNA appears to be responsible of intestinal pseudo-obstruction (PMID: 18854860))
    Genotype/Phenotype correlations females with unbalanced X-limited rearrangements show in most cases complete skewing of X-inactivation and a normal phenotype ; translocation of Xq28 onto an autosome leads to functional disomy and abnormal phenotype in all cases; copy-number gains between two low copy repeats (LCRK1 and LCRL1) are associated with the incidence of hypoplasia of the corpus callosum PMID: 22528406