Question 1

A patient recently diagnosed with CF comes into your office. The patient states that they have had difficulty breathing and have been feeling dizzy and light-headed. The patient is concerned that these symptoms are related to their CF. Which system is primarily affected by patients with Cystic Fibrosis?

Accepted Answer

The pulmonary/respiratory, digestive, and reproductive systems are typically most affected by Cystic Fibrosis. The most common cause of morbidity in CF is pulmonary disease; additionally, chronic pulmonary infections occur in most patients with CF.. An individual with CF produces thick mucous secretions that clog that airways, increasing the likelihood of infection and making it harder to breathe.

Question 2

Among which population is CF the most common lethal inherited disorder?

Accepted Answer

The ACMG recommends that all Caucasians of non-Jewish descent and Ashkenazi Jews get screened, but CF is still the most common lethal inherited disorder among Caucasians in the U.S.

Question 3

A 25 y/o patient with a history of Cystic Fibrosis comes in complaining of a productive cough, fever, chills, and shortness of breath. Upon physical exam, the patient has dullness to percussion, and increased tactile fremitus. Based on these findings, what are the two most common shapes you are likely see on gram stain and culture?

Accepted Answer

S. aureus (Gram + cocci in clusters) and P. aeruginosa (Gram - rods) are the most common causes of pneumonia in patients with CF. Gram + cocci in pairs indicate an infection with S. pneumo, which is not the most likely organism to cause pneumonia in a patient with CF.

Question 4

A 28 y/o male patient with a history of Cystic Fibrosis comes into your office with his wife. They are trying to conceive and are having difficulty. Which of the following information would you tell your patient?

Accepted Answer

Congenital absence of the vas deferens as well as other reproductive structures results in the absence of spermatozoa. While it is possible that his wife may be infertile, most males with CF are infertile due to the absence of this reproductive structure.

Question 5

A woman who is a carrier for the CF gene marries a man who is also a carrier of the gene. They come in to see you because they are trying to get pregnant and want to know the likelihood of having an offspring with CF. What will you tell them?

Accepted Answer

CF is inherited in an autosomal recessive pattern. If both parents are carriers, the risk of inheriting the CFTR mutation and developing CF is 25%, or 1 in 4.

Question 6

Which types of gene mutations represent a majority of CF mutations, ultimately leading to the wide variety of clinical phenotypes in patients with Cystic Fibrosis?

Accepted Answer

Nonsense mutations, frameshift mutations, and splice site mutations, in addition to deletions of the CFTR gene result in complete absence of functioning of CFTR and make up a majority of the mutations.

Question 7

The mother of a young boy with Cystic Fibrosis presents to your office. She would like to know if there is anything that can be done to improve the symptoms her son experiences as a result of his CF. Which of the following medications can help improve quality of life in patients with CF?

Accepted Answer

All of the above medications can be given to a patient with CF in order to improve quality of life. Albuterol is a bronchodilator which allows opening up of the airways in the lungs making it easier for the patient to breathe. Guanfenesin is a decongestant which draws water into the bronchi thinning the mucous and lubricating the airway to help facilitate removal of the mucous, and antibiotics help kill bacteria that excess mucous harbors in the lungs preventing future lung infections.

Question 8

Which of the following gene mutations are associated with CF?

Accepted Answer

It is a mutation of the CFTR gene which results in absence of functional CFTR leading to CF mutations. There are no GTFR or FTFR gene mutations associated with CF.

Question 9

Chloride channels are disrupted in patients with Cystic Fibrosis. What implications does this have on ion transport, water, and airway clearance?

Accepted Answer

Defective chloride transport and enhanced sodium absorption lead to a net increase in water absorption, thinned airway surface liquids, and decreased ciliary clearance.

Question 10

Which aspect of the pathophysiology of CF is responsible for failure to thrive in patients with CF?

Accepted Answer

Failure to thrive is a common finding in children with CF because of malabsorption related to pancreatic insufficiency, as well as increased caloric expenditure, and chronic infection. The endocrine pancreas becomes fibrotic reducing insulin secretion and islet cells. Biliary cirrhosis, Cor pulmonale, and Meconium ileus are not responsible for failure to thrive in patients with CF.

Quiz 13: Cystic Fibrosis