Fragile-X Diagnoses in Children with Autism

Fragile-X and Autism

Autism is a very wide spectrum from which multiple other disorders hang that a child could be diagnosed with, including Rett, Asperger's, PDD-NOS, and Fragile-X. The new DSM-V, as of May 2013, does not include separate categories for these, absorbing some under the simple umbrella of ASD. Fragile-X is not one of these.

What is Fragile-X?
Fragile X syndrome (FXS) is the most common known cause of an inherited intellectual disability. It is also the most common known genetic cause of autism or autism spectrum disorders. What was once labeled "mental retardation" would be considered part of FXS, where delays in speech and language development are common, as well as a variety of physical and behavioral characteristics. FXS is caused by a “full mutation” of the FMR1 gene, one which makes a very important protein called FMRP (fragile X mental retardation protein) that is abundant on the edge of nerve cells called dendrites- the site at which point the nerves communication with one another.

Autism spectrum disorders have been found to be greatly affected by abnormalities within the sex chromosomes (47, XXY, 47 XYY, 45,X/46,XY mosaicism), particularly the X chromosome. Many autism-related disorders had genetic mutations from the mother's chromosome, including Fragile X, Rett, and Klinefelter syndrome. the FMR1 gene is located on the X chromosome itself, where the genetic mutation causes the intellectual abnormalities. The fact that FXS is understandable and able to be tested clearly, linking it to the genetic mutation, makes it an easier disorder to diagnose and treat than autism alone. The latter is a complex combination of different characteristics that are hard to pin down to a few genetic markers, albeit knowing well that a large part of it is either inherited or through mutation when looking at prevalence among twins.


In terms of prevalence:

  • About 1 in 3,600 to 4,000 are males
  • About 1 in 4,000 to 6,000 are females

Women have the opportunity to be screened before pregnancy, in order to test for Fragile-X in themselves. Both in men and women, the disorder might not manifest severely, with only mild symptoms available that are often ignored. The problems is that oftentimes, women won't realize they are carriers of the genetic mutation until they give birth to a babe in whom the expressions are more apparent, and sometimes quite severe.

Fragile X in the Family
Using data from a survey of 1,099 families who have a child with Fragile X syndrome, a study published in the American Journal on Intellectual and Developmental Disabilities examined adaptation across 7 dimensions of family life: parenting knowledge, social support, social life, financial impact, well-being, quality of life, and overall impact. It came to the conclusion that although families report a high quality of life, they struggle with simple areas such as social support, social life, and parenting knowledge. In essence, family resources and social supports moderate the disorder's effects on quality of life and well-being.

Understanding why Fragile X and Autism Shuns Physical Contact
Anis Contractor, assistant professor of physiology at Feinberg and lead investigator of a 2010 study published in the Journal Cell, found that for those with the defect, the part of the brain that is responsible for response to touch, called the sensory cortex, is slower to develop during a critical period of growth when the brain is very plastic and rapidly changing. If the elements of the rapid development are uncoordinated, the brain is wired incorrectly and cannot function properly. Loss of the FMR1 gene abilities means that the brain is unable to develop as it should and meet its milestones in a timely fashion, which would also account to some never managing to do so.

Additional Reference:
National Fragile X Foundation


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