Mosaicism in Fragile X syndrome: A family case series

Wilmar Saldarriaga, Laura Yuriko González-Teshima, Jose Vicente Forero-Forero, Hiu Tung Tang, Flora Tassone

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Fragile X syndrome (FXS) has a classic phenotype, however its expression can be variable among full mutation males. This is secondary to variable methylation mosaicisms and the number of CGG triplet repeats in the non-coding region of the Fragile X Mental Retardation 1 (FMR1) gene, producing a variable expression of the Fragile X Mental Retardation Protein (FMRP). Here we report a family with several individuals affected by FXS: a boy with a hypermethylated FMR1 mutation and a classic phenotype; a man with an FMR1 gene mosaicism in the range of premutation (PM) and full mutation (FM), who has a mild phenotype due to which FXS was initially disregarded; and the cases of four women with a FM and mosaicism. This report highlights the importance of DNA molecular testing for the diagnosis of FXS in patients with developmental delay, intellectual disability and/or autism due to the variable phenotype that occurs in individuals with FMR1 mosaicisms.

Original languageEnglish (US)
JournalJournal of Intellectual Disabilities
StateAccepted/In press - 2021


  • FMR1
  • CGG repeat expansion disease
  • Fragile X syndrome
  • mosaicism

ASJC Scopus subject areas

  • Health Professions (miscellaneous)
  • Psychiatry and Mental health


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