BackgroundPopulation screening for FMR1 mutations has been a topic of considerable discussion since the FMR1 gene was identified in 1991. Advances in understanding the molecular basis of fragile X syndrome (FXS) and in genetic testing methods have led to new, less expensive methodology to use for large screening endeavors. A core criterion for newborn screening is an accurate understanding of the public health burden of a disease, considering both disease severity and prevalence rate. This article addresses this need by reporting prevalence rates observed in a pilot newborn screening study for FXS in the US.MethodsBlood spot screening of 14,207 newborns (7,312 males and 6,895 females) was conducted in three birthing hospitals across the United States beginning in November 2008, using a PCR-based approach.ResultsThe prevalence of gray zone alleles was 1:66 females and 1:112 males, while the prevalence of a premutation was 1:209 females and 1:430 males. Differences in prevalence rates were observed among the various ethnic groups; specifically higher frequency for gray zone alleles in males was observed in the White group compared to the Hispanic and African-American groups. One full mutation male was identified (>200 CGG repeats).ConclusionsThe presented pilot study shows that newborn screening in fragile X is technically feasible and provides overall prevalence of the premutation and gray zone alleles in the USA, suggesting that the prevalence of the premutation, particularly in males, is higher than has been previously reported.

The prevalence of Fragile X Syndrome (FXS) is 1 in 4000 in males and 1 in 2500 in males and females, respectively, in the general population. Several screening studies aimed at determining the prevalence of FXS have been conducted in individuals with intellectual disabilities (IDs) with a prevalence varying from 1.15% to 6.3% across different ethnic groups. A previous study in Indonesia showed an FXS prevalence of 1.9% among the ID population. A rapid, effective, and inexpensive method for FMR1 screening, using dried blood spots capable of detecting an expanded FMR1 allele in both males and females, was recently reported. We used this approach to screen 176 blood spots, collected from Central Java, Indonesia, for the presence of expanded FMR1 gene alleles. Samples were collected from high-risk populations: 112 individuals with ID, 32 obtained from individuals with diagnosis of autism spectrum disorders, and 32 individuals with a known family history of FXS. Fourteen subjects carrying an FMR1 expanded allele were identified including 7 premutations (55-200 CGG repeats) and 7 full mutations ( > 200 repeats). Of the seven subjects identified with a full mutation, one subject was from a nonfragile X family, and six from were families with a history of FXS.Introduction F ragile X syndrome (FXS), with a prevalence of 1:2500 to 1:4000 in the general population (Turner et al., 1996;Crawford et al., 2002;Hagerman, 2008), is the most common genetic cause of intellectual disability (ID) and the leading genetic cause of autism. Although prevalence estimates vary across studies, there is agreement that the risk of autism spectrum disorders (ASD) is higher in FXS than in many other neuro-developmental disorders. From recent studies, *2% to 6% of children with ASD have FXS (Li et al., 1993;Wassink et al., 2001;Estecio et al., 2002;Hagerman, 2002;Reddy, 2005), and *30% of children with FXS have ASD (see Appendix in Rogers et al., 2001;Kaufmann et al., 2004); Pervasive Developmental Disorder-Not Otherwise Specified is seen in an additional 30% (Harris et al., 2008). In fact, FXS is characterized by a broad spectrum of behavioral and emotional impairment, psychological problems, and learning disabilities in those without mental retardation or ID. In addition, specific physical features such as long face, macrognathia, prominent ears, hyperextensible joints, flat feet, and macroorchidism in puberty are observed (Hagerman et al., 1991;Lachiewicz and Dawson, 1994;Giangreco et al., 1996). The milder phenotypes are not accounted for in the current prevalence figures (Tassone et al., 1999;Hagerman, 2006). In addition, significant phenotypic involvement has emerged in some individuals with the premutation (55-200 CGG repeats), including fragile X-associated premature ovarian insufficiency (FXPOI) in females, and fragile X-associated tremor/ataxia syndrome (FXTAS) in both male and female aging carriers Sullivan et al., 2005). Prevalence for premutation alleles was *1 in 110-250 for females and 1 in 250-800 for males (Rousseau et al., 199...

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