This study was designed to explore the behavioral phenotype of autism in a group of young children with fragile X syndrome (FXS). Twenty-four children with FXS, ages 21 to 48 months, were compared with two well-matched groups: 27 children with autism (AD) and 23 children with other developmental delays (DD), on two standardized autism instruments, as well as on measures of development and adaptive behavior. Two FXS subgroups emerged. One subgroup (n = 16) did not meet study criteria for autism. Their profiles on the autism instruments and the developmental instruments were virtually identical to the other DD group. The other FXS subgroup (n = 8, or 33% of the total FXS group) met study criteria for autism. Their profiles on the autism instruments were virtually identical to the group with autism. The finding of two FXS subgroups raises a hypothesis of additional genetic influences in the FXS autism group, warranting further genetic studies.
Department of Psychiatry, University of Colorado Health Sciences Center, Denver, Colorado (ROGERS, WEHNER)
M.I.N.D. Institute and Department of Pediatrics, University of California Davis, Davis, California (HAGERMAN)
Address for reprints: Sally J. Rogers, Ph.D., JFK Partners, University of Colorado Health Sciences Center, 4200 East 9th Avenue/Campus Box C234, Denver, CO 80262; e-mail: Sally.Rogers@uchsc.edu.
Acknowledgments. This work was partially supported by National Institute of Child Health and Human Development (NICHD) Grant PO1 HD35468. Dr. Rogers was also supported by Maternal and Child Health Bureau Grant (MCHB) 2T73MC00011-04 and by the Administration on Developmental Disabilities Grant 90DD0414. Dr. Hagerman was also supported by NICHD Grant HD36071 and by MCHB Grant MCJ-089413. The ongoing help of the Developmental Psychobiology Research Group is gratefully acknowledged, as is the assistance of Ms. Teneke Warren and Ms. Cynthia Uhlhorn with manuscript preparation.