Question

Case Studies,

Chapter 10, Fetal Development and Genetics

1. Lauren has been a pediatric nurse at a children’s hospital for the past 7 years. Recently she began a new job as a nurse in a genetics office. One of today’s cases involves Emily and Brad Davis. Emily is a young white female who looks to be in her mid-twenties. Her husband, Brad, is a young white male. Lauren notices the young woman is pregnant, most likely sometime in her mid-trimester. (Learning Objectives 4 and 6)

Lauren introduces herself and explains that she needs to obtain a complete medical history from the couple. When the history is complete, Lauren finds the following pertinent facts:

1. Emily, age 27, and Brad, age 29, have been married for 6 years.
2. They have a 4-year-old daughter who was recently diagnosed with cystic fibrosis.
3. Emily is currently 28 weeks pregnant.
4. The couple is very worried that their unborn child may have cystic fibrosis.
5. No person in either immediate family has cystic fibrosis.
6. A cousin on Emily’s mom’s side of the family has cystic fibrosis.
7. Brad has no known cases of cystic fibrosis in his family; however, he recalls a great uncle on his dad’s side who was ill most of his life and died at age 9.

1. What type of genetic disorder does cystic fibrosis fall under? Why doesn’t Emily, Brad, or any of their siblings have this disorder? What are the odds that the Davises' unborn child will have this disorder?

2. What would you tell the Davis couple about planning for future children?

3. What do you think about the history of the great uncle who died at age 9?

2. Abbie and her husband, Greg, come to your genetics center for additional testing after having had a “positive” maternal serum alfa protein test (MSAFP) at 16 weeks gestation and a “positive” triple screen test at 18 weeks gestation. Abbie is now 20 weeks pregnant. (Learning Objectives 4, 5, and 6)

1. Based on the “positive” MSAFP, what genetic abnormality could the fetus have? What more would we want to know about her “positive” test result? What does the “positive” triple screen test indicate?

2. What additional genetic testing is indicated for Abbie and Greg? Which tests could be definitive? What is your role as the nurse in regards to genetic counseling?

3. Abbie and Greg are given the diagnosis of trisomy 21. They want to know what caused this and what it means to their baby. What ethical and legal issues does this diagnosis raise?

Answer 1

1. A. CF is an inherited disorder from autosomal recessive type and it occurs when mutations happens on both the copies of gene cystic fibrosis transmembrane conductance regulator protein or CFTR. Those that happen to have a single allele must be the carrier type.

This is because emily, brad and their siblings possess only one copy of the gene and the this gene is a recessive type so in order to get the disorder the children must inherit two copies of this gene one from each parent. So emily, brad are healthy parents and does not show the symptoms of this disease but are carriers for this recessive type and can inherit to the next generation.

Davise's unborn child have a 1 in 4 (25%0 chance of developing this disorder since both parents are carriers and hence there is this chance if the child inherit two non functional genes, 1 from each parent to develop this disease.

B. Its best to advice them about the awareness and chances of having a child with CF since both are carriers. So they have to decide the best and get prepared for this chance.

C. The great uncle could have been a person with CF disorder. There are chances of developing this since they have it in their family. And the non hispanic white race possess this disorder than any other race so its likely that he died from this disease.

2. A. Based on the postive msafp, it measures the level of alpha protein which is produced by the fetus. Abnormal and positive levels indicates neural tube defects such as spina bifida or down's syndrome which is confirmed by amniocentesis. It can also be anenchephaly in which the brain is not properly developed. Positive triple screen test indicates the presence of AFP, HCG, and estriol. Positive means high levels of this protein can indicate neural tube defects or failure of fetus abdomen to close.

B. Additional genetic testing can be amniocentesis and chorionic villus sampling to confirm the disorder in fetus. Genetic counseling includes generating the family history to find the potential risk and hereditary risk. If indicated genetic testing can be done through blood or saliva sample to evaluate the risk and eliminate the cases of false positive results.

It creates a series of ethical questions related to quality of life, choice of baby, etc.. Reproductive choice is one of the issues involved.

C. The common cause of downs syndrome is trisomy 21. This means there are 47 chromosomes instead of 46. Error in cell division called non-dysjunction causes trisomy 21. It leaves a sperm or egg cell with a extra copy of chromosome 21 before or at the time of conception. This baby is having a genetic disorder which includes birth defects, learning disability, and facial features. Down's syndrome also have heart defects and problems with hearing and vision.  Since the disorder is not life threatening to the baby the complications of abortion are involved and can induce maternal versus fetal rights.