Fragile X syndrome (FXS) is a genetic disorder associated with mental retardation and in milder forms learning disabilities and emotional problems without significant cognitive deficits (Hagerman and Hagerman 2002
). FXS affects all races, with an estimated prevalence rate of approximately 1:3600 (Crawford, Meadows et al. 2002
). The syndrome results from an unstable expansion of trinucleotide (CGG) repeat in the 5’ untranslated regions of the fragile X mental retardation 1 (FMR1
) gene, leading to a deficient production of the fragile X mental retardation protein (FMRP), an essential element for brain development and functioning (Loesch, Huggins et al. 2004
). A normal FMR1
gene has 5-44 CGG repeats, while the abnormal expansion is classified into intermediate or gray zone (45-54 repeats), premutation (55-200 CGG repeats) and full mutation (more than 200 repeats) (Maddalena, Richards et al. 2001
). A mix pattern of full mutation and premutation is termed mosaicism. The full mutation is associated with lower levels or absence of FMRP causing cognitive impairment and other behavioral abnormalities. Mosaicism is associated with milder cognitive impairment than the full mutation and better development of adaptive skills (Loesch, Huggins et al. 2004
). The premutation can cause mild clinical involvement such as anxiety, attention deficit hyperactivity disorder (ADHD), executive function deficits, premature ovarian failure, and late onset tremor and ataxia (FXTAS)(Farzin, Perry et al. 2006
), (Hagerman and Hagerman 2004
). Individuals with FXS typically have physical and neurobehavioral symptoms. Physical features often include long face with prominent ears, flat feet, hyperextensible joints, high arched palate, macroorchidism, mitral valve prolapse, and strabismus. Neurobehavioral symptoms include social anxiety (shyness), gaze avoidance, repetitive behavior such as hand flapping and hand biting, sensory hypersensitivity, tactile defensiveness, delayed speech development, echolalia, and poor motor coordination (Hagerman and Hagerman 2002
),(Belmonte and Bourgeron 2006
Autism is present in several genetic disorders such as FXS, tuberous sclerosis, Rett syndrome and phenylketenuria (Dykens E.M. 1997
). The prevalence rate of autism in FXS ranges between 21% to 33% (Hatton, Sideris et al. 2006
), (Bailey, Mesibov et al. 1998
), (Kaufmann, Cortell et al. 2004
), (Rogers, Wehner et al. 2001
). In addition, many individuals diagnosed with FXS without autism present some autistic-like behaviors such as eye gaze avoidance, sensory sensitivity, atypical language and repetitive behavior (Hatton, Sideris et al. 2006
). Several studies reported that individuals diagnosed with FXS and autism have lower cognitive abilities (Cohen 1995
), (Turk and Graham 1997
), (Kaufmann, Cortell et al. 2004
) lower developmental scores (Rogers, Wehner et al. 2001
) as well as lower adaptive behavior levels and problem behavior (Hatton, Hooper et al. 2002
); (Kau, Tierney et al. 2004
) than individuals with FXS without autism.
Although there is a body of knowledge about the cognitive and behavioral abilities of individuals with FXS and autism, there is a gap in the literature regarding the motor abilities of this population. There are only two studies that examined motor functioning of individuals with FXS with and without autism. Baranek and colleagues (Baranek, Danko et al. 2005
) compared the sensory-motor features of children with FXS, autism and other developmental delays during the first year of life and found unusual motor patterns such as posturing and repetitive leg movement as discriminating features of FXS at 9-12 months. Rogers and colleagues (Rogers, Wehner et al. 2001
) compared toddlers with FXS and autism, FXS without autism, autism without FXS, and other developmental disabilities on the Mullen Scales of Early Learning (Mullen 1995
). They found differences between the FXS and autism group and the other three groups on all the Mullen scales except the Visual Reception scale. Consistently, the FXS groups had lower scores on the motor scales.
Intact development of motor skills enables infants, toddlers and children to explore their environment and engage in meaningful physical and social interactions. Various studies in children with autism reported a deficit in the organization of the action towards a goal (Barthelemy, Adrien et al. 1994
), presentation of movement disturbances during early infancy (Teitelbaum, Teitelbaum et al. 1998
), significant effect of IQ on the postural deficit (Minshew, Sung et al. 2004
), as well as poor motor control causing poor fine and gross motor skills. There have been no similar studies regarding children with FXS, although these children are characterized by low tone and endurance that affect their motor development, and predispose them to have difficulties in self-care activities, play, academic skills, and social participation.
The purpose of this study is: 1) to describe the motor abilities of young children diagnosed with FXS both with and without and autism. 2) To compare the motor scores of these two groups. Our research question is: Are the motor abilities of children diagnosed with both FXS and autism different from those of children with FXS without autism. We hypothesize that children with FXS with autism will exhibit poorer performance on the Mullen motor scales than children with FXS alone, when removing the effect of their cognitive abilities, by controlling for the visual reception score of the Mullen.