Emergence of developmental delay in infants and toddlers with an fmr1 mutation

Anne C. Wheeler*, Angela Gwaltney, Melissa Raspa, Katherine C. Okoniewski, Elizabeth Berry-Kravis, Kelly N. Botteron, Dejan Budimirovic, Heather Cody Hazlett, David Hessl, Molly Losh, Gary E. Martin, Susan M. Rivera, Jane E. Roberts, Donald B. Bailey

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


BACKGROUND: Children with FMR1 gene expansions are known to experience a range of developmental challenges, including fragile X syndrome. However, little is known about early development and symptom onset, information that is critical to guide earlier identification, more accurate prognoses, and improved treatment options. METHODS: Data from 8 unique studies that used the Mullen Scales of Early Learning to assess children with an FMR1 gene expansion were combined to create a data set of 1178 observations of >500 young children. Linear mixed modeling was used to explore developmental trajectories, symptom onset, and unique developmental profiles of children ,5 years of age. RESULTS: Boys with an FMR1 gene full mutation showed delays in early learning, motor skills, and language development as young as 6 months of age, and both sexes with a full mutation were delayed on all developmental domains by their second birthday. Boys with a full mutation continued to gain skills over early childhood at around half the rate of their typically developing peers; girls with a full mutation showed growth at around three-quarters of the rate of their typically developing peers. Although children with a premutation were mostly typical in their developmental profiles and trajectories, mild but significant delays in fine motor skills by 18 months were detected. CONCLUSIONS: Children with the FMR1 gene full mutation demonstrate significant developmental challenges within the first 2 years of life, suggesting that earlier identification is needed to facilitate earlier implementation of interventions and therapeutics to maximize effectiveness.

Original languageEnglish (US)
Article numbere2020011528
Issue number5
StatePublished - May 1 2021

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health


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