Mosaicism in Fragile X syndrome: A family case series

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 varia...

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Bibliographic Details
Published in:Journal of intellectual disabilities 2022-09, Vol.26 (3), p.800-807
Main Authors: Saldarriaga, Wilmar, González-Teshima, Laura Yuriko, Forero-Forero, Jose Vicente, Tang, Hiu-Tung, Tassone, Flora
Format: Article
Language:English
Subjects:
Autism
Deoxyribonucleic acid
Diagnostic tests
DNA
Foreign Countries
Fragile X syndrome
Genetic Disorders
Genotype & phenotype
Heredity
Intellectual disabilities
Intellectual Disability
Males
Medical diagnosis
Mutation
Symptoms (Individual Disorders)
Women
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Summary: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.
ISSN:1744-6295
1744-6309
DOI:10.1177/1744629521995346