Pathophysiology—Down Syndrome

Introduction

Down Syndrome is a chromosomal disorder that can produce a range of intellectual and physical defects in the individual. Depending on the phenotypic variation, these defects can be more or less severe for some than they are for others (Karmiloff-Smith et al., 2016). It is the most common genetic disorder in the U.S. and the most common cause of learning in young children. It can also lead to other health-related issues and complications such as heart as well as gastrointestinal disorders (Mayo Clinic, 2018). This paper will discuss the pathophysiology of Down Syndrome; the signs, symptoms and complications of the disorder; what current research and evidence-based practices focus on; and the most common treatment and management practices for Down Syndrome.

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Pathophysiology

In all but 5% of cases, Down Syndrome is caused by trisomy 21—i.e., the individual has three chromosome 21 copies (Antonarakis, Lyle, Dermitzakis, Reymond & Deutsch, 2004). As human cells typically have 23 chromosome pairs, with the father and mother each contributing a chromosome to the pair, any disruption in this pairing leads to a genetic disorder in the development of the child. Down Syndrome is caused by a disruption in the 21st chromosome: the cell of this chromosome abnormally divides; the result is that more genetic material is developed than is needed and that can negatively impact the features of the child and the development of the child’s cognitive abilities in some cases.

While Trisomy 21, or three full copies of chromosome 21, is most commonly the cause of Down Syndrome for about 95% of the cases, other forms are possible: Mosaic Down Syndrome and Translocation Down Syndrome are the two other possibilities. In the former, the extra copy of chromosome 21 is only found in a few of the child’s cells rather than in all. In the latter, chromosome 21 attaches to a separate chromosome. Currently, the exact cause of this disruption in chromosome 21 is unknown (Mayo Clinic, 2018). However, risk factors that have been identified include the age of the mother at conception—the risk is greater when the woman is over the age of 35.

Signs, symptoms and complications

Diagnoses can be made before as well as after birth. Signs of intellectual disability may indicate Down Syndrome, as most individuals with this genetic disorder display some form of cognitive impairment. Language learning is often delayed and memory skills are typically impacted. Signs and symptoms that are most often recognized include facial deformities—such as having a flattened face, small head, shortened neck, spots on the iris of the eye, and upward slanting eyelids. Shortness of height is another common sign, along with short fingers and small hands plus poor muscle tone.

Complications that can stem from Down Syndrome include: heart trouble, gastrointestinal trouble, immune disorders, sleep apnea, obesity, spinal issues, leukemia and dementia. Heart complications are the most common, as 50% of individuals with Down Syndrom also have some form of heart defect as well. However, life expectancies for children with Down Syndrome have increased and most adults can expect to live beyond their 60s (Mayo Clinic, 2018).

Current research and evidence based practices

Current research is examining how different phenotypic expressions of down syndrome occur (Karmiloff-Smith et al., 2016). Understanding variations in Down Syndrome is believed to be a step in understanding how to treat it and if it is possible to prevent it. The research, so far, has not provided any definitive answers to prevention, which means treatment and management are the only options available to families at the time being. Evidence-based practice indicates that genetic counseling can help parents decide if they are at high risk or low risk for having a child with Down Syndrome (Mayo Clinc, 2018).

Treatment and management

Treatment of children with Down Syndrome focuses mainly on identifying the disorder and addressing any complications that may arise, whether they are physical or cognitive. Down Syndrome children can go on to have normal functioning lives, so long as the severity of the disorder is not too severe. In most cases, cognitive treatment and management is effective in assisting the child to overcome learning difficulties and develop appropriately over time (Karmiloff-Smith et al., 2016).

Conclusion

Down Syndrome is a genetic disorder that has no known cause: it occurs in chromosome 21 when an extra copy is created in 95% of the cases—but what triggers the extra copy creation is still a mystery. Risk factors include older age of the mother at conception. Behavioral and environmental factors, though, have not been found to be impactful. Down Syndrome cannot be prevented based on current evidence of the disorder, though researchers are looking into understanding the variations that occur and what triggers them. Treatment and management through cognitive therapy and physical monitoring are the only options for this disorder.

References

Antonarakis, S. E., Lyle, R., Dermitzakis, E. T., Reymond, A., & Deutsch, S. (2004).

Chromosome 21 and down syndrome: from genomics to pathophysiology. Nature Reviews Genetics, 5(10), 725.

Karmiloff-Smith, A., Al-Janabi, T., D’Souza, H., Groet, J., Massand, E., Mok, K., … &

Tybulewicz, V. (2016). The importance of understanding individual differences in Down syndrome. F1000Research, 5.

Mayo Clinic. (2018). Down Syndrome. Retrieved from

https://www.mayoclinic.org/diseases-conditions/down-syndrome/symptoms-causes/syc-20355977