Basic information for topics, such as “What is it?” is available in the About FXTAS section. Answers to other frequently asked questions (FAQs) specific to FXTAS are in this section.
Some medical conditions are reported to be associated with the FMR1 premutation, but only in men. These include:
- Abnormal heart rhythm (arrhythmia)
- Balance disorders1
- Congestive heart failure
- High blood sugar
- Sleep apnea2
- Mood disorders, including major depressive disorder, anxiety disorder, and post-traumatic stress disorder
High blood pressure is also associated with FXTAS in both men and women, but it seems to be more common among women with the FMR1 premutation.
Premutation genes—the kind associated with FXTAS and characterized by 55 to 199 extra CGG sequences in the FMR1 gene—can grow spontaneously from generation to generation. That is, the gene's CGG sequences can increase in number on their own. They can even expand to the level of full mutation (200 or more CGG sequences), making fragile X syndrome more likely.
The FMR1 premutation form is more likely to expand depending on the number of CGG repeats it has. The greater the number, the greater the risk of expansion. Risk also increases with each passing generation.
Read more about how FMR1 changes as it is passed from parent to child.
Before NICHD-supported researchers discovered FXTAS in 2001, it was often misdiagnosed. The symptoms of FXTAS—memory loss, tremors, muscle stiffness or rigidity, a shuffling gait or walk, and slowed speech—are similar to Alzheimer's disease and Parkinson's disease symptoms.
A characteristic of FXTAS is also ataxia, which means clumsiness of movement or loss of coordination that is not due to muscle weakness. Ataxia is most often caused by loss of function in the cerebellum, the part of the brain that controls the body's coordination. It can also be caused by problems with the motor sensory pathways leading in and out of the cerebellum.4 Although symptoms of FXTAS are similar to those of other conditions, its diagnosis is unique due to the white matter lesions (areas of dead cells) in the cerebellum.
- Leehey, M. A. (2009), Fragile X-associated tremor/ataxia syndrome (FXTAS): clinical phenotype, diagnosis and treatment. Journal of Investigative Medicine, 57, 830–836.
- Hamlin, A., Liu, Y., Nguyen, D. V., Tassone, F., & Hagerman, R. J. (2011). Sleep apnea in fragile X premutation carriers with and without FXTAS. American Journal of Medical Genetics, 156B. Retrieved May 30, 2012, from http://www.ncbi.nlm.nih.gov/pubmed/21932336
- National Institute of Child Health and Human Development. (2006). How is fragile X syndrome inherited? Retrieved May 30, 2012.
- Hagerman, R. J. Genotype-phenotype relationships in fragile X families. Retrieved August 21, 2012, from https://reporter.nih.gov/project-details/8064264