NursingDiscussion postDifferential diagnosis

NR 507 Week 2: cystic fibrosis and post-viral cough

Part one hides a question about race and medicine that most posts answer badly — ancestry shifts the prior probability, it does not remove a diagnosis, and saying that clearly is the difference between a good post and a careless one.

Aug 15, 2026

Editorial process

Last reviewed · August 15, 2026

Written by

Aaron Bishop

MA, Education

assignment interpretation and research-methods coaching across disciplines

Reviewed by

Dr. Nathan Cole

PhD, Rhetoric & Composition

Argumentation and thesis development

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Interpret the task
Assignment instructions
Deliverables
Proposed outline
Research plan
Reference shortlist
Final review

Two respiratory cases, two different traps

Part one's findings are close to pathognomonic once you read them together: an infant who is small for age with a huge appetite, foul-smelling greasy stools, wheeze and cough is describing malabsorption plus airway disease, which is cystic fibrosis until proven otherwise. The prompt still wants three differentials with the weaknesses of each, so build them honestly — coeliac disease explains the steatorrhoea and failure to thrive but not the wheeze and is unusual before gluten exposure; Shwachman-Diamond syndrome gives pancreatic insufficiency but typically with neutropenia; a primary immunodeficiency or primary ciliary dyskinesia explains recurrent respiratory infection but not the fat malabsorption. Naming the weakness is half the mark. For testing, the sweat chloride test is the answer, with CFTR genotyping alongside it and faecal elastase to confirm pancreatic insufficiency; note that newborn screening may already have flagged this, and say what a negative newborn screen would and would not rule out in a child who now looks like this.

The age-of-onset question has a genotype answer. Later presentation usually means residual CFTR function — class IV or V mutations that produce a channel which conducts poorly rather than one that never reaches the membrane — so the phenotype is milder and the pancreas is often spared. Then the ancestry question, which is the one to handle carefully. Cystic fibrosis is less common in people of African ancestry, so the prior probability falls and you would weight alternatives more heavily; it does not fall to zero, the disease occurs in every population, and the mutation spectrum differs enough that a panel testing only common European variants can miss it. Say all three things. Part two is Tammy: three weeks of deep productive cough after a cold, no fever, no rhinorrhoea now. Acute bronchitis leads, with pertussis, post-nasal drip and cough-variant asthma as the differentials that matter, and green sputum is not evidence of bacterial infection.

Likely learning objectives

Inferred from the brief — check these against your own rubric.

01
Construct a differential in which each candidate is paired with the finding it fails to explain.
02
Connect CFTR mutation class to age of onset and disease severity.
03
Reason about ancestry as a modifier of prior probability rather than as a rule-out.
04
Distinguish post-viral bronchitis from the causes of chronic cough that require different management.

Assignment instructionsQuoted verbatim

Read the full question

Review every instruction before using the planning guidance that follows.

Discussion NR507 Wk2 Rhinorrhea Case Discussion Discussion: NR507 Wk2 Rhinorrhea Case Discussion NR 507 Week 2 Discussion: PART No. 1: A five-month-old Caucasian female is brought into the clinic as the parent complain that she has been having ongoing foul-smelling , greasy diarrhea. She seems to be small for her age and a bit sickly but, her parent’s state that she has a huge appetite. Upon examination you find that the patient is wheezing and you observe her coughing. · Write a differential diagnosis of at least three (3) disorders and explain why each might be a possibility and any potential weaknesses of each differential. · Why is it that the later in age this disease manifest itself, the less severe the disease is? · What tests would you run to clarify your differential and potentially come to a definitive diagnosis? · If the same child was African in ancestry would this change your initial differential? Why or why not? NR507 Wk2 Rhinorrhea Case Discussion PART No. 2: Tammy is a 33-year-old who presents for evaluation of a cough. She reports that about 3 weeks ago she developed a “really bad cold” with rhinorrhea. The cold seemed to go away but then she developed a profound, deep, mucus-producing cough. Now, there is no rhinorrhea or rhinitis—the primary problem is the cough. She develops these coughing fits that are prolonged, very deep, and productive of a lot of green sputum. She hasn’t had any fever but does have a scratchy throat. Tammy has tried over-the-counter cough medicines but has not had much relief. The cough keeps her awake at night and sometimes gets so bad that she gags and dry heaves. · Write a differential of at least three (3) possible diagnosis’s and explain how each may be a possible answer to the clinical presentation above. Remember, to list the differential in the order of most likely to less likely. · Based upon what you have at the top of the differential how would you treat this patient? · Suppose now, the patient has a fever of 100.4 and complains of foul smelling mucous and breath. Indeed, she complains of producing cups of mucous some days. She has some trouble breathing on moderate exertion but this is only a minor complaint to her. How does this change your differential and why? à Bronchiectasis p. 1256 can happen after an infection. NR507 Wk2 Rhinorrhea Case Discussion. PART No. 3: A nursing student comes into your office because they are struggling with the concept of pulmonary function. They know you as an experienced FNP and so they are comfortable asking if you could clarify the terms residual volume (RV), functional reserve capacity (FRC), total lung capacity (TLC) inspiratory reserve volume (IRV), and expiratory reserve volume (ERV). 1. Give her a definition of each? 2. List three (3) disorders that can alter the residual volume and explain how they do so? NR 507 Week 2 Quiz (CH 3, 34-36 + 8 – 13 from week 1) 1. At the arterial end of capillaries, fluid moves from the intravascular space into the interstitial space because the (Points : 2) Discussion NR507 Wk2 Rhinorrhea Case Discussion 2. Physiologic pH is maintained around 7.4 because bicarbonate (HCO3) and carbonic acid (H2CO3) exist in a ratio of (Points : 2) 3. When thirst is experienced, how are osmoreceptors activated? (Points : 2) 4. Chvostek sign and Trousseau sign indicate (Points : 2) 5. Which are indications of dehydration? (Points : 2) 6. In hyperkalemia, cardiac rhythm changes are a direct result of (Points : 2) 7. Water movement between the intracellular fluid compartment and the extracellular compartment is primarily a function of (Points : 2) 8. In tuberculosis, the body walls off the bacilli in a tubercle by stimulating (Points : 2) 9. Pulmonary edema usually begins at a pulmonary capillary wedge pressure or left atrial pressure of _____ mm Hg. (Points : 2) 10. Which inflammatory mediators are produced in asthma? (Points : 2) 11. The most successful treatment for chronic asthma begins with (Points : 2) 12. Which pleural abnormality involves a site of pleural rupture that act as a one-way valve, permitting air to enter on inspiration but preventing its escape by closing during expiration? (Points : 2) 13. _____ is a fulminant form of respiratory failure characterized by acute lung inflammation and diffuse alveolocapillary injury. (Points : 2) 14. In ARDS, alveoli and respiratory bronchioles fill with fluid as a result of the (Points : 2) 15. Clinical manifestations that include unexplained weight loss, dyspnea on exertion, use of accessory muscles, and tachypnea with prolonged expiration are indicative of (Points : 2) 16. Clinical manifestations of pulmonary hypertension include (Points : 2) 17. Dyspnea is not a result of (Points : 2) 18. High altitudes may produce hypoxemia through (Points : 2) 19. Chest wall compliance in infants is _____ in adults. (Points : 2) 20. What is the primary cause of RDS of the newborn? (Points : 2) 21. An accurate description of childhood asthma is that it is a(n) (Points : 2) 22. Cystic fibrosis (CF) is caused by a(n) (Points : 2) 23. Which of the following statements about the advances in the treatment of RDS of the newborn is incorrect? (Points : 2) 24. Which of the following types of croup is most common? (Points : 2) 25. Which immunoglobulin is present in childhood asthma? (Points : 2)

Turn the brief into deliverables

01
Three or more differentials for part one, each with a stated weakness.
02
An explanation of the onset-severity relationship at genotype level.
03
A named diagnostic test pathway.
04
An explicit, careful answer to the ancestry question.
05
A differential, reasoning and plan for part two, with APA citations throughout.

Differentials, weaknesses, tests, then the ancestry question

Build the infant differential

Give three or more candidates and pair each with the finding it cannot explain.

Genotype and age of onset

Explain residual CFTR function and mutation class as the reason later presentation is milder.

The diagnostic pathway

Name sweat chloride testing, genotyping and faecal elastase, and note newborn screening.

Ancestry and prior probability

State that incidence differs, that the diagnosis is not excluded, and that mutation panels may under-detect.

Tammy's post-viral cough

Diagnose acute bronchitis, give the differentials that change management, and address sputum colour.

Sources for CFTR genetics and post-viral cough

Recommended databases

NCBI Bookshelf (StatPearls)
PubMed Central
National Heart, Lung, and Blood Institute
CINAHL

Search sequence

1.
Fix the CFTR mutation classes before writing the onset question — the answer depends on knowing what each class does to the protein.
2.
Search for cystic fibrosis incidence and mutation spectrum by ancestry, so the fourth question rests on data rather than on impression.
3.
Confirm current guidance on antibiotics in acute bronchitis, since the sputum-colour point needs a citable source.
4.
Look up adult pertussis presentation, which is easy to miss and is the differential with the biggest consequence.

Reference shortlist

These are authoritative starting points, not a ready-made bibliography. A qualified reviewer must confirm that each source fits the assignment and supports the claim beside which it is cited.

Nothing here is cleared for citation until you have read it.

01
Cystic Fibrosis
StatPearls, NCBI Bookshelf · 2023
Pathophysiology, mutation classes and the diagnostic pathway, which carries the first three questions of part one.
02
Cystic Fibrosis - What Is Cystic Fibrosis?
National Heart, Lung, and Blood Institute · 2024
An institute-level summary useful for incidence and for the plain-language framing of the ancestry answer.
03
Acute Bronchitis
StatPearls, NCBI Bookshelf · 2023
Diagnosis and management of acute bronchitis, including why sputum colour does not indicate bacterial infection.
04
Antimicrobial resistance
World Health Organization · 2023
Supports the argument against reflexive antibiotics in part two with the population-level consequence.

Review before submission

Common mistakes

Listing differentials without stating what each one fails to account for, which the prompt asks for by name.
Answering the ancestry question with either 'no, race is irrelevant' or 'yes, it rules it out' — both are wrong.
Explaining later onset by environment when the question is about residual channel function.
Treating green sputum in part two as evidence for antibiotics.
Forgetting pertussis in an adult with a three-week paroxysmal cough.

Submission checklist

Does every differential come with its weakness?
Have you named the sweat chloride test and said what confirms pancreatic insufficiency?
Is the ancestry answer nuanced — lower prior, not exclusion, plus the panel-coverage point?
Did you include pertussis in Tammy's differential?
Are both parts supported by scholarly citations in APA format?

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