Fragile x Syndrome Essay Assignment

Fragile x Syndrome Essay Assignment

Fragile X Syndrome: A Case Discussion

According to the CDC (2020), Fragile X Syndrome (FXS) is the most commonly known cause of inherited intellectual disability. Fragile X syndrome occurs in approximately 1 in 4,000 males and 1 in 8,000 females, (NIH,2020). It is an X-linked inherited disorder that causes cognitive impairments as well as distinct physical characteristics. The syndrome affects the CNS, the testes, and the cranial skeleton.

The case given is, patient L.A. has a 3-year-old boy with developmental delay and small joint hyperextensibility. She has been diagnosed with fragile X-associated mental retardation and is currently 14 weeks pregnant. Screening to identify the sex of the baby as well as genetic testing is vital, as this information will assist the Nurse practitioner in counseling the patient appropriately on what to expect and providing early intervention and support.  Given that her first child has the disorder, there is a 50% chance that her second child will be affected.  If her baby is a boy, the clinical manifestations will be more severe; A girl may only exhibit subtle impairments.   In this paper, the pathogenesis and the clinical manifestations of fragile X syndrome will be discussed. Fragile x Syndrome Essay Assignment

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Fragile X Genetic Mutation

Mutations in the FMR1 gene produces Fragile X syndrome. The FMR1 gene, also known as the Fragile X mental retardation gene locus, is found on the X chromosome, where it is most fragile, hence the name Fragile X.  At the beginning of the FMR1 gene, there is a trinucleotide sequence, known by the letters CGG, in individuals who are neither infected nor carriers, the CGG repeat is fewer than 50. CGG repeats greater than 200 results in abnormal chemical changes, known as methylation. This aberration results in a full mutation of the FMR1 gene. This mutation prevents the production of FMRP. FRMP is a protein found in tissues of the brain and testes and is needed for healthy development. In the absence of the FMRP protein, cognitive disabilities and some discernable physical features occur. Since the disorder is X linked, the mutation of the FMR1 gene is fully expressed in males. Males carry only one copy of the x chromosome.  In males with Fragile X syndrome, the abnormal x linked chromosome does not have another X chromosome to balance out the abnormality, resulting in the disorder’s full expression. Females have two X chromosomes, therefore, a mutation in one X chromosome will not present with the same severity, as the other X chromosome compensates for the defective chromosome (Stone et al., 2020).

Clinical Syndromes of Fragile X

The loss of function of the FMR1 protein causes an alteration in the neuronal synapse development, resulting in developmental delay and cognitive disabilities by 1-2 years, as seen in Ms. Anderson’s 3yr old son.  Patients with Fragile X may also present a plethora of behavioral issues, including hyperactivity and autistic behaviors (Stone et al., 2020).  These manifestations are more pronounced in males than females.  The physical characteristics of the syndrome in males may not become apparent until late in childhood or early adolescence. These physical characteristics include the coarsening of facial features, large ears, a long face, crossed eyes, and a large head. Affected males will also start to exhibit large testes.

Other clinical manifestations of the syndrome may include joint laxity, scoliosis, recurrent, and otitis media.  Adults with Fragile X syndrome may also suffer from cardiac problems such as mitral valve prolapses, seizures. Autism spectrum disorder is also a common sequela of Fragile X syndrome (Stone et al., 2020). fragile x syndrome essay assignment

Heredity

Parent

As mentioned earlier, Fragile X syndrome is an X-linked disorder. In X-linked disorders, males are affected, while females may exhibit subtle characteristics; some females will not show any signs of disorder but carry the affected gene. Regarding the case of Ms. Anderson, given that her first son exhibits signs of Fragile X, she is likely to be a carrier of the affected gene.  Males inherit the X chromosome from their mothers, and the Y chromosomes from their fathers, therefore, in the case of Ms. Anderson, she is the source of the mutation. If her baby is a boy, there is a 50% chance he will be affected, and if it is a girl, she will be a carrier of the disorder. fragile x syndrome essay assignment

Grandparents

        The family history is unremarkable, which means no other males in the family exhibited any characteristics associated with the disorder. With this knowledge, Ms. Anderson’s mother was likely a carrier of the gene. Given that females carry X X chromosomes combination, Ms. Anderson would have received one X chromosome from her father and another X chromosome from her mother. If she had received the defective X chromosome from her father, he would have been phenotypically affected. Since her family history suggested otherwise, therefore, it is unlikely that Ms. Anderson inherited Fragile X from her father, which leaves the other X chromosome inherited from her mother. We now know that females can carry the gene without showing signs of the disorder.   The additional X chromosome made up of the loss of function of the defective chromosome. As a result, Ms. Anderson’s mother was not phenotypically affected but carried the gene fragile x syndrome essay assignment.

Siblings

Any offspring of Ms. Anderson will have the FMR1 gene mutation, as it is passed on via the X chromosome. However, a female child will present with a milder form of the illness, if any. All male siblings will be affected because they will receive the only one and defective copy of the X chromosome from their mother.

There may be other factors that can affect the presentation of the gene in the offspring. Recent studies have shown an AGG interruption in the CGG repeats of the defective gene reduces the chances of having a full mutation of the FMR1 gene (Nolin, et al., 2015). This discovery highlights the importance for patients to undergo genetic testing to thoroughly analyze the risk of carrying another child with Fragile X syndrome. Diagnosis of the illness is made through molecular genetic testing of FMR1 gene. The gene is characterized by the number of CGG repeats a person will have. Prenatal diagnostic testing involves Chorionic villus sampling and amniocentesis fragile x syndrome essay assignment. These tests will determine if a fetus has inherited the gene.

Conclusion

Fragile X Syndrome is an inherited disorder. It is known to be a common cause of intellectual disability. Patients who carry the gene should be counseled for the likelihood that their children will also have the disorder. Considering that it is an X linked disorder, the severity of the manifestations depends on the gender of the offspring.  In the case of Lisa Anderson, she is a genetic carrier of Fragile X syndrome. Her first male child already presents with the clinical manifestations of the disorder. There is a 50% chance another male child will also be affected. If her second offspring is female, she may present normal or with only mild features of the disorder.

Fragile X syndrome can go undiagnosed. Therefore, a thorough family history assessment should be done.  If one or more family member is found to have behavioral or physical characteristics indicative of the disorder, genetic counseling should be recommended. In the case of Ms. Anderson, genetic counseling will provide her with information on the disorder’s inheritance, implications, testing, and available resources.  It will also help her to adjust to the diagnosis as well as have realistic expectations. Fragile x Syndrome Essay Assignment

 

References

Ciaccio, C., Fontana, L., Milani, D., Tabano, S., Miozzo, M., & Esposito, S. (2017). Fragile X syndrome: a review of clinical and molecular diagnoses. Italian Journal Of Pediatrics, 43(1). https://doi.org/10.1186/s13052-017-0355-y

National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention. (n.d.). Fragile X syndrome: Learning what families need, one person at a time. Center For Disease Control and Prevention. Retrieved August 14, 2020, from https://www.cdc.gov/ncbddd/fxs/features/learning-what-families-need.html

Nolin, S. L., Glicksman, A., Ersalesi, N., Dobkin, C., Brown, W. T., Cao, R., Blatt, E., Sah, S., Latham, G. J., & Hadd, A. G. (2015). Fragile X full mutation expansions are inhibited by one or more AGG interruptions in premutation carriers. Genetics in medicine: official journal of the American College of Medical Genetics, 17(5), 358–364. https://doi.org/10.1038/gim.2014.106

National Institute of Health. (2020, August 4). Fragile X Syndrome. https://ghr.nlm.nih.gov/condition/fragile-x-syndrome

Stone, W., Basit, H., & Los, E. (2020). StatPearls [Ebook] (p. Fragile X Syndrome). StatPearls Publishing. Retrieved 4 August 2020, from https://www.ncbi.nlm.nih.gov/books/NBK459243/.  fragile x syndrome essay assignment

 

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