Developmental profiles of infants with anFMR1premutation.
BACKGROUND
Emerging evidence suggests that a subset ofFMR1premutation carriers is at an increased risk for cognitive, emotional, and medical conditions. However, because the premutation is rarely diagnosed at birth, the early developmental trajectories of children with a premutation are not known.


METHODS
This exploratory study examined the cognitive, communication, and social-behavioral profiles of 26 infants with a premutation who were identified through participation in a newborn screening for fragile X syndrome pilot study. In this study, families whose newborn screened positive for anFMR1premutation were invited to participate in a longitudinal study of early development. Twenty-six infants with the premutation and 21 matched, screen-negative comparison babies were assessed using validated standardized measures at 6-month intervals starting as young as 3 months of age. The babies were assessed up to seven times over a 4-year period.


RESULTS
The premutation group was not statistically different from the comparison group on measures of cognitive development, adaptive behavior, temperament, or overall communication. However, the babies with the premutation had a significantly different developmental trajectory on measures of nonverbal communication and hyperresponsivity to sensory experiences. They also were significantly more hyporesponsive at all ages than the comparison group. Cytosine-guanine-guanine repeat length was linearly associated with overall cognitive development.


CONCLUSIONS
These results suggest that infants with a premutation may present with subtle developmental differences as young as 12 months of age that may be early markers of later anxiety, social deficits, or other challenges thought to be experienced by a subset of carriers.
RTI International, 3040 E. Cornwallis Road, P.O. Box 12194, Research Triangle Park, NC 27709 USA.
Anne C
AC
Wheeler
University of North Carolina at Chapel Hill, Chapel Hill, NC USA.
John
J
Sideris
Davis MIND (Medical Investigation of Neurodevelopmental Disorders) Institute, University of California at Davis, Davis, CA USA ; Department of Pediatrics, University of California at Davis, Davis, CA USA.
Randi
R
Hagerman
Rush University Medical Center, Chicago, IL USA.
Elizabeth
E
Berry-Kravis
Davis MIND (Medical Investigation of Neurodevelopmental Disorders) Institute, University of California at Davis, Davis, CA USA.
Flora
F
Tassone
RTI International, 3040 E. Cornwallis Road, P.O. Box 12194, Research Triangle Park, NC 27709 USA.
Donald B
DB
Bailey
Early development; FMR1 premutation; Newborn screening