Page Contents
OVERVIEW
This page is dedicated to organizing various examples of standardized exam questions whose answer is Cystic Fibrosis (CF). While this may seem a odd practice, it is useful to see multiple examples of how CF will be characterized on standardized exams (namely the boards and the shelf exams). This page is not meant to be used as a traditional question bank (as all of the answers will be the same), however seeing the classic “test” characterization for a topic is quite valuable.
KEY CHARACTERISTICS OF THIS CONDITION (ON EXAMS)
When it comes to standardized exams, each topic has its own “code” marked by key buzzwords, lab findings, clues, etc. If you are well versed in this code you will be able to more quickly identify the condition that is being discussed, and get the right answer on the exam you are taking. Below is the “code” for CF.
Chief Complaints:
- Cough/fever/productive cough: essentially symptoms of a respiratory infection (often pneumonia)
- Failure to thrive: patients not growing
- Diarrhea (large greasy stools): steatorrhea (caused by pancreatic insufficiency)
Patient History:
- Young child: often this condition is noted in younger children given the severity of symptoms.
- Failure to pass meconium: in babies
- Recurrent respiratory infections: pneumonia, sinusitis
- Family history of similar symptoms: patients may have siblings or other relatives with similar symptoms.
Clinical Workup
- Failure to thrive: low percentiles for height and weight (in babies and children)
- Cyanosis/clubbing can be noted on the physical exam.
- Nasal polyps are a common exam finding
- Colonization with Pseudomonas aeruginosa is very commonly seen in this patient population.
- Interstitial changes can be seen on an X-ray
- Increased sweat chloride concentration on the skin and be measured (and is helpful for diagnosis)
QUESTION EXAMPLES
Question # 1
A 3 year old girl gets admitted to the hospital because of failure to thrive. Her parents explain that she often has large greasy stools. They have noticed these for the past 4 months. This child was born a term after an uncomplicated pregnancy, and weighted 7 lb at delivery. She did not pass meconium until the age of 3 days. She is below the 5th percentile for both height and weight. A physical examination shows a decreased amount of soft tissue mass. Her lungs are clear to auscultation. The abdominal exam is unremarkable. Later it is discovered that the patient has exocrine pancreatic insufficiency which is the cause of her failure to thrive. What is a possible diagnosis that explains this clinical picture?
Explanation # 1
Failure to thrive + greasy stools + delayed meconium + exocrine pancreatic insufficiency = CF
Question # 2
A 13 year old boy recently has started snoring very loudly. He has a past medical history that is remarkable for respiratory tract infections and steatorrhea. Nasal polyps are found in this patient which explain his snoring. What is the underlying condition that this patient likely suffers from?
Explanation # 2
Respiratory tract infections + steatorrhea + nasal polyps = CF
Question # 3
A 7 year old boy is brought to the clinic because of not feeling well for the past few days. He has a fever, cough, and sputum production. When he was a newborn an examination was unremarkable and showed no abnormalities. He has had a history of respiratory problems since infancy. His temperature is 98.6°F, pulse is 98/min, and respiration’s are 34/min. Pulse oximetry shows a saturation of 85% on room air. A physical exam shows clubbing, cyanosis around the lips, and a hyper inflated chest. Auscultation reveals diffuse rhonchi bilaterally as well as wheezing at the end of expiration. A chest X-ray is shown and shows hyperinflation of the lungs, scattered atelectasis, and interstitial changes. What is the likely diagnosis in this patient?
Explanation # 3
History of respiratory tract infections + clubbing/cyanosis + hyperinflation/interstitial changes on X-ray = CF
Question # 4
A 18 month old male is borough to the clinic because he has been having a cough and fever for the past couple of days. He has had a history of similar episodes of symptoms since he was 3 months old. He is in the 20th percentile for height, and below the 5th percentile for weight. His temperature is 100.6°F, pulse is 145 ppm, and respirations are 36/min. A physical exam reveals mild clubbing, and there are also wheezes and crackles at the slung bases bilaterally. An X-ray of the chest shows the presence of streaky densities on both sides, and there is mild hyperinflation. What is the likely diagnosis in this patient?
Explanation # 4
History of respiratory tract infections + failure to thrive (low percentiles) + clubbing + hyperinflation/interstitial changes on X-ray = CF
Question # 5
A 13 year old male is brought to the physician because he has chronic diarrhea. He also has had difficulty gaining weight appropriately. He has a past history of recurrent respiratory infections, and in the past sputum cultures have been positive for gram negative bacteria that has prompted treatment with antibiotics. He has a younger brother that has died from respiratory infections at the age of 7. What is the likely diagnosis in this patient?
Explanation # 5
Chronic diarrhea + failure to thrive + recurrent respiratory infections + family history of similar infections = CF
Question # 6
A 5 year old male is borough to the clinic because he has been having a worsening productive cough for the past 2 days. Last hear he was found to have pulmonary infiltrates, and was diagnosed with a pneumonia on a chest X-ray. Since then, the patient has had 3 more cases of pneumonia, each that have required antibiotics in order to improve symptoms. Currently his chest X-ray reveals bilateral infiltrates of the lower lobes. He is also found to have high chloride content in his sweat. What is the diagnosis in this patient?
Explanation # 6
History of recurrent respiratory infections + high chloride content in sweat = CF
Question # 7
A 16 year old male is admitted to the hospital because of a fever, cough, and hypoxemia. The patient has received IV antibiotics and frequent chest physiotherapy, however his condition continues to worsen. Sputum cultures grow out Pseudomonas aeruginosa. The patient passes away after a few days due to an overwhelming pneumonia and respiratory failure. His past medical history reveals that he has been postalized in the past for recurrent episodes of sinusitis, pneumonia, and poor growth. An autopsy reveals findings of distention and obstruction of the pancreatic ducts, and that both of his vas deferens are absent. What is the likely diagnosis in this patient?
Explanation # 7
History of recurrent respiratory infections + history of poor growth + pancreatic disease (likely causing pancreatic insufficiency + absence of vas deferens = CF
Question # 8
A 4 year old male is borough to the pediatrician because he has had a productive cough and fever for the past week. A physical exam reveals an ill appearing child who has rales auscultated in the left lower lung. A chest X-ray reveals the presence of a left lower lobe pneumonia, and the patient is admitted to the hospital for IV antibiotics. His past medical history is notable for 3 prior episodes of pneumonias, and both his height and weight are noted to be in the bottom 5th percentile. Further testing is notable for a high sweat chloride level. What is the likely diagnosis in this patient?
Explanation # 8
History of recurrent respiratory infections + history of poor growth + high sweat chloride level = CF
Question # 9
A 5 year old male is colonized with Pseudomonas species in his repository tract. His sweat chloride concentration is 110 mEq/L (reference range is < 60 mEq/L). What is the diagnosis in this patient?
Explanation # 9
High sweat chloride level = CF
Question # 10
A 10 year old male is brought to the physician by his father because he has had a productive cough, wheezing, and exertional shortness of breath of the past year. He also has a history of recurrent repository tract infections since his birth. Currently he is in the 20th percentile for both his height and weight. His father comments that he has noticed that the patient’s younger siblings have also started to develop similar symptoms. A physical exam is notable for mild clubbing of fingers. Lab studies are notable for increased sweat chloride and sodium levels. What is the diagnosis in this patient?
Explanation # 10
Recurrent respiratory tract infections + low height and weight percentiles + increased sweat chloride = CF
TESTABLE FACTS ABOUT THIS TOPIC (BEYOND ITS IDENTIFICATION)
Many questions on standardized exams go beyond simply recognizing the underlying topic. Often there are specific testable facts regarding some aspect of the topic’s pathophysiology/management/clinical implications that are commonly asked. Some of these are listed below:
Cause:
- Mutations on the CFTR gene (chromosome 7)
- Most common mutation: Δ508 mutation (deletion of Phe508). Leads to a misfoleded protein that is retained in the rough endoplasmic reticulum and NOT transported to the cell membrane. This leads to decreased chloride secretions.
- Inheritance pattern: autosomal recessive
Complications:
- Infertility: congenital absence of the vas deferens occurs much of the time with CF (rendering males infertile).
- Pancreatic insufficiency: due to pancreatic duct obstruction/inflammation/fibrosis
- Hyponatremia (in the setting of high temperature/exercise): Patient secrete sweats with higher then normal concentrations of sodium and chloride. They can lose a significant amount of sodium this way!
Treatment:
- Pancreatic lipase can be given to help with pancreatic insufficiency
Page Updated: 04.19.2017