Artstract created by Ren Lind
There are many different theories as to the causes of Autism, however, Fragile X Syndrome is a direct cause for an estimated 2-6% of Autism cases. [1] Theories for other causes include genetics, environmental factors, the communication between neurons being disrupted, and others, but today we’ll be focusing on Fragile X.
Fragile X Background
Fragile X Syndrome (FXS) is an inherited genetic disorder. It gets its name from the X chromosome appearing “fragile” compared to a typical X chromosome, as figure 1 depicts.
FXS individuals have a mutation on the FMR1 gene. This gene is responsible for making a protein that manages and develops synapses between neurons. Synapses are where communication between neurons gets passed along and important messages can be spread to the brain, or the body so bodily processes can happen.
This gene mutation can lead to behavioral and social challenges, intellectual deficits, alterations in physical features, anxiety, and delayed speech and learning in childhood, among other symptoms. Typically, FXS is diagnosed between 12 months and 3.5 years old, but it can be diagnosed later in life. Symptoms of FXS greatly overlap with symptoms presented in Autism Spectrum Disorder.
Autism Background
Autism Spectrum Disorder (ASD) is characterized by social deficits and repetitive motions or interests throughout life. [4] Symptoms such as social anxiety, avoiding eye contact, social impairment, and other diagnostic symptoms overlap between FXS and ASD.
FXS causes Autism because the symptoms presented can be the same, depending on which symptoms the individual with FXS displays. It’s important to note that not all people with FXS will be diagnosed with ASD because they may have different symptoms than those of Autism. However, about 60% of males with FXS have Autism, and 20% of females with FXS have Autism. [5]
ADHD and Seizures Co-occurring
Interestingly, there are also comorbidities of Attention-Deficit/Hyperactivity Disorder (ADHD) and seizure for people with Fragile X and Autism. Around 50% of people with Fragile X and ASD also have ADHD. [6]
Summary
Autism has many theorized causes and risk factors, but Fragile X Syndrome is a confirmed cause for a small percentage of Autism cases. This occurs because Fragile X can present the same way as Autism, creating an overlap between the conditions, however, not every person with Fragile X will have the same symptoms as Autism.
Resources
[1] Rajaratnam, A., Shergill, J., Salcedo-Arellano, M., Saldarriaga, W., Duan, X., & Hagerman, R. (2017). Fragile X syndrome and fragile X-associated disorders. F1000Research, 6, 2112. https://doi.org/10.12688/f1000research.11885.1
[2] Image from https://healthjade.net/fragile-x-syndrome/
[3] Rajaratnam, A., Shergill, J., Salcedo-Arellano, M., Saldarriaga, W., Duan, X., & Hagerman, R. (2017). Fragile X syndrome and fragile X-associated disorders. F1000Research, 6, 2112. https://doi.org/10.12688/f1000research.11885.1
[4] Dicarlo, G., Wallace, M. (2022). Modeling dopamine disfunction in autism spectrum disorder: from invertebrates and vertebrates. Neuroscience and Biobehavioral Reviews, 133. https://doi.org/10.1016/j.neubiorev.2021.12.017
[5, 6, 7] Rajaratnam, A., Shergill, J., Salcedo-Arellano, M., Saldarriaga, W., Duan, X., & Hagerman, R. (2017). Fragile X syndrome and fragile X-associated disorders. F1000Research, 6, 2112. https://doi.org/10.12688/f1000research.11885.1
[8] Dicarlo, G., Wallace, M. (2022). Modeling dopamine disfunction in autism spectrum disorder: from invertebrates and vertebrates. Neuroscience and Biobehavioral Reviews, 133. https://doi.org/10.1016/j.neubiorev.2021.12.017
