Mosaicism in Fragile X syndrome: A family case series. (September 2022)

• Record Type: Journal Article
• Authors: Saldarriaga, Wilmar; González-Teshima, Laura Yuriko; Forero-Forero, Jose Vicente; Tang, Hiu-Tung; Tassone, Flora
• Is Part Of: Journal of intellectual disabilities. Volume 26:Number 3(2022)
• Page Start: 800
• Page End: 807
• Publication Date: 2022-09
• Subjects: FMR1 -- Fragile X syndrome -- mosaicism -- CGG repeat expansion disease; Mental retardation -- Periodicals; People with mental disabilities -- Periodicals; Learning disabilities -- Periodicals; Handicap intellectuel; Trouble d'apprentissage; Handicapé mental; Périodique électronique (Descripteur de forme); Ressource Internet (Descripteur de forme); 362.1968588
• DOI: 10.1177/1744629521995346
• Languages: English
• ISSNs: 1744-6295

Abstract

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.