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Updated: May 7, 2026

A Robust Polymerase Chain Reaction-based Assay for Quantifying Cytosine-guanine-guanine Trinucleotide Repeats in Fragile X Mental Retardation-1 Gene
08:22

A Robust Polymerase Chain Reaction-based Assay for Quantifying Cytosine-guanine-guanine Trinucleotide Repeats in Fragile X Mental Retardation-1 Gene

Published on: September 16, 2019

Think about it: FMR1 gene mosaicism

Francesca Andrea Bonarrigo1, Silvia Russo2, Paola Vizziello3

  • 1Pediatric Clinic 1, Department of Pathophysiology and Transplantation, University of Milan Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.

Journal of Child Neurology
|September 26, 2013
PubMed

Insights

Fragile X syndrome (FXS), a common cause of intellectual disability, can present with mild symptoms. This case highlights rare FMR1 gene mosaicism, emphasizing the need for early diagnosis in subtle cases.

Area of Science:

  • Genetics
  • Neurodevelopmental Disorders
  • Molecular Biology

Background:

  • Fragile X syndrome (FXS) is a leading genetic cause of intellectual disability and autism.
  • It typically results from CGG trinucleotide repeat expansion in the FMR1 gene, leading to protein dysfunction.

Observation:

  • A 4-year-old boy presented with mild psychomotor delay and no significant dysmorphic features.
  • Molecular analysis revealed a rare mosaic pattern in the FMR1 gene, with one normal and one fully mutated allele.

Findings:

  • The patient's FMR1 gene analysis demonstrated mosaicism for repeat size and methylation.
  • This rare genetic finding in FXS underscores the variability of clinical presentation.

Implications:

  • Physicians should consider FXS in patients with even mild developmental delays.
  • Early diagnosis is crucial for effective patient rehabilitation and informed family planning.
Keywords:
fragile X syndromeintellectual disabilitymosaicism

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