This page is setup to help others with a basic understanding of Fragile X Syndrome and how it affects our family. It should by no means be taken as medical advice.
Fragile X Syndrome (FXS) is a genetic disorder carried on the X chromosome. It is passed from father to daughter, and sometimes from mother to child. The disorder is caused by a mutation in a gene on the X chromosome. The gene responsible for Fragile X Syndrome is called the FMR1 gene. The mutation occurs in the DNA of the X chromosome and is defined by the number of repeats of a pattern of DNA called CGG repeats. A CGG repeat of less than 60 is considered a normal gene, 60-200 CGG repeats is considered premutation gene, and greater than 200 repeats is considered a full mutation of the gene which causes FXS. The full mutation of the gene causes the gene to shut down or methylate a region of the FMR1 gene. Normally, this gene produces a protein called FMRP, but once it becomes methylated the protein is either no longer produced or produced in smaller amounts depending on the methylation status of the gene. The lack of this specific protein causes Fragile X Syndrome.
Basic DNA and FXS:
In females, these are two X chromosomes (XX); in males they are and X and Y (XY). When a couple reproduces, each parent passes one of their genes to the baby. Thus, a mother will give one X to a baby and a father will either give an X or a Y. If the mother has FXS in either it's premutation or full mutation form, she has a 50% chance of passing the FXS chromosome to her child (remember, she has one affected and one unaffected chromosome). If the father has FXS in either it's premutation or full mutation form he will always pass it to his daughters but never to his sons.
Premutation of FXS in an individual makes them a carrier of FXS. A premutation is 60-200 CGG repeats. Carriers of FXS have a chance of passing FXS to their children and in passing, the CGG repeat usually expands.
Mutation of FXS in an individual makes them fully affected by FXS. A full mutation is <200 CGG repeats. As with carriers, affected individuals have a chance of passing FXS to their children and in passing the CGG repeat usually expands. Once an individual has over 200 CGG repeats, the FMR1 gene begins to shut down and stop producing the protein FMRP. In some individuals that are fully affected, FMRP is still produced, but in smaller quantities. This is known as methylation mosacism or incomplete methylation. Below are some of the most common FXS characteristics (Taken from Akron Children's Hospital Parents' Notebook)
• Eye and vision impairments
• Large testicles (evident after puberty)
• Elongated face
• Low muscle tone
• Flat feet
• Prominent ears
• High arched palate
• Recurrent ear infections
• Approx. 20% will develop seizure disorder
• Gastroesophageal reflux (causes gagging and regurgitation)
• Hyper-extensible joints (double jointed)
• Anxiety and shyness
• Language delays
• Autism and autistic-like behavior
• Poor eye contact
• Hyperactivity and short attention span
• Sensory integration difficulties
• Tactile defensiveness (negative response to touch)
• Hand biting and hand flapping
• Perseveration (repetition of same actions or words)
In addition to these scientifically documented characteristics, anecdotal strengths noted by parents are listed below. These strengths can be used to help meet the challenges of living with fragile X syndrome.
• Loving nature
• Eager to please
• Love of music and dancing
• Full of laughter and life
• Finds comfort in structure and routines
• Complete honesty
• Good imitators
What this means for our family:
I am a carrier of FXS with a premutation of the gene. I have a chance to pass FXS along to any children that I have, and in passing it could either become a full mutation or be a premutation. Because only one of my X chromosomes is affected, that chance of passing FXS is 50%.
Ayden is fully affected by FXS with incomplete methylation. His body is still producing some of the protein FMRP which is sometimes associated with a less severe case of FXS. We find this to be true with Ayden, though it is not with all individuals. He does have many of the symptoms and behaviors associated with FXS children, but because it manifests so differently in each person we are unable to say exactly when or if he will catch up to normal development.
Emma is fully affected by FXS and has one fully methylated gene. Things are a little different with her as she has one fully functional gene as well. We're unsure where she will stand in regards to development at this time, but so far she is developing as is expected for a neuro-typical child. You can read about this more in depth at this blog post: What Does It All Mean?
To learn more about Fragile X Syndrome, please visit The National Fragile X Foundation Website or the FRAXA Research Foundation Website.
You can also read Parent's Notebook put out by the Akron Children's Hospital Fragile X Program.