Cytogenetic Testing Case Examples

1

You are seeing a baby who has classical features of Down syndrome (trisomy 21). To confirm the diagnosis and facilitate accurate genetic counseling for the family, which of the following is the best test to order?

1.5

You are caring for a baby in the NICU with: dysmorphic features (broad, flat nasal bridge and a high forehead), history of intrauterine growth restriction, hypotonia, cleft palate, and seizures. The NICU team already ordered FISH (for chromosomes 13/18/21/X/Y), karyotype, and microarray. Match the following results to the test:

Draggable item		Corresponding Item
Normal and consistent with a male with no evidence of aneuploidy for chromosomes 13, 18, 21, X, or Y.		FISH
46,XY,del(4)(p16.3)		Karyotype
1.9 Mb deletion from 4p16.3		Microarray

1

Given the baby’s features and the results of the cytogenetic testing (see previous question), what is this baby’s diagnosis?

1

Another infant with the same diagnosis is transferred to your NICU. In her records, you see that the diagnosis was made based on metaphase FISH targeted to the 4p16.3 region which identified a deletion of this region. Her parents want to know the recurrence risk for future pregnancies, so you recommend __________ for each of them. 

Explain your answer using the "Show Your Work" tool. 

1.5

You are seeing a patient who has Tetralogy of Fallot, cleft palate, hypocalcemia, and dysmorphic features. Microarray identified a 2.5 Mb deletion. Additional cytogenetic tests were also ordered. What do you expect the results of each of these tests to be?

Interphase FISH for chromosomes 13/18/21/X/Y
Metaphase FISH targeted to the same region identified by microarray
High resolution karyotype

Normal
Abnormal (deletion identified)

1

Based on the patient's features and the cytogenetic test results, what deletion syndrome do you think was identified?

1

For the tests you predicted to have normal results in question 5, why would they NOT detect the deletion?

1

For a future patient with the same features, if you could only order ONE cytogenetic test, which would you order?

Explain your answer using the "show your work" section.

1

You have a patient with multiple congenital anomalies who has a terminal 18q deletion and a terminal 8p duplication. Her parents had microarrays to test for the copy number variants and both were normal. What do you tell the parents? Explain your answer using the Show Your Work tool

You are seeing a baby who has classical features of Down syndrome (trisomy 21). To confirm the diagnosis and facilitate accurate genetic counseling for the family, which of the following is the best test to order?

Given the baby’s features and the results of the cytogenetic testing (see previous question), what is this baby’s diagnosis?

You are seeing a patient who has Tetralogy of Fallot, cleft palate, hypocalcemia, and dysmorphic features. Microarray identified a 2.5 Mb deletion. Additional cytogenetic tests were also ordered. What do you expect the results of each of these tests to be?

Based on the patient's features and the cytogenetic test results, what deletion syndrome do you think was identified?

For the tests you predicted to have normal results in question 5, why would they NOT detect the deletion?

For a future patient with the same features, if you could only order ONE cytogenetic test, which would you order? Explain your answer using the "show your work" section.

You have a patient with multiple congenital anomalies who has a terminal 18q deletion and a terminal 8p duplication. Her parents had microarrays to test for the copy number variants and both were normal. What do you tell the parents? Explain your answer using the Show Your Work tool

For a future patient with the same features, if you could only order ONE cytogenetic test, which would you order?

Explain your answer using the "show your work" section.