What is the diagnosis for a patient with persistent cough and shortness of breath?

Diagnostic Approach to Persistent Cough and Shortness of Breath

First, immediately rule out life-threatening conditions including pneumonia, pulmonary embolism, congestive heart failure, and foreign body aspiration, particularly if the patient has acute onset, fever, hemoptysis, or significant weight loss. 1

Initial Critical Assessment

Determine the duration of cough to guide your diagnostic pathway:

• Acute cough (<3 weeks): Consider pneumonia, pulmonary embolism, respiratory tract infection, or exacerbation of underlying conditions (COPD, asthma, bronchiectasis) 1
• Subacute cough (3-8 weeks): Most likely postinfectious cough, upper airway cough syndrome (UACS), transient bronchial hyperresponsiveness, or pertussis 1, 2, 3
• Chronic cough (>8 weeks): Systematically evaluate for the "big four" causes: UACS, asthma, gastroesophageal reflux disease (GERD), and nonasthmatic eosinophilic bronchitis (NAEB) 1, 4, 5

Essential History Elements

Obtain these specific details that directly impact diagnosis:

• Medication review: ACE inhibitor use causes cough in a significant proportion of patients and should be stopped immediately if present 1, 6
• Smoking status: Current or former smoking suggests chronic bronchitis or COPD as the etiology 1
• Red flag symptoms: Hemoptysis, significant weight loss (>10 lbs), fever, night sweats, or voice changes mandate immediate chest imaging and consideration of malignancy or tuberculosis 3, 5
• Timing of onset: Abrupt onset suggests foreign body aspiration, which can present with persistent cough and dyspnea 1, 7
• Associated symptoms: Sinus congestion/postnasal drip points to UACS; heartburn/regurgitation suggests GERD; wheezing indicates asthma 1, 2

Diagnostic Algorithm for Chronic Cough with Dyspnea

Follow this sequential approach, as multiple causes often coexist:

Step 1: Evaluate and Treat UACS First

• Start with first-generation antihistamine/decongestant combination (e.g., brompheniramine/pseudoephedrine) as first-line therapy 1, 2
• Add intranasal corticosteroids if nasal congestion is prominent 2
• Monitor elderly patients carefully for urinary retention, sedation, increased intraocular pressure, and worsening hypertension 2
• Response typically occurs within 1-2 weeks if UACS is the cause 1

Step 2: If Cough Persists, Evaluate for Asthma

• Obtain spirometry with bronchodilator response testing 1, 6
• If spirometry is normal but asthma is still suspected, perform bronchoprovocation challenge testing 1
• If testing unavailable, initiate empiric trial of inhaled corticosteroids plus bronchodilators 1, 4
• Consider cough-variant asthma even without wheezing 4, 6

Step 3: If Still Unresolved, Address NAEB and GERD

• For NAEB: Obtain induced sputum for eosinophils; if unavailable, trial oral corticosteroids 1
• For GERD: Initiate empiric proton pump inhibitor therapy without testing if reflux symptoms present 1, 6
• GERD treatment may require 2-3 months for full response 1

Step 4: Advanced Evaluation if Refractory

• Obtain chest CT scan to evaluate for uncommon causes including bronchiectasis, interstitial lung disease, or malignancy 1, 5
• Consider bronchoscopy if CT suggests endobronchial lesion or foreign body 1, 7
• Refer to pulmonologist or cough specialist 1, 5

Special Populations and Considerations

Immunocompromised patients (HIV, transplant, chemotherapy): Expand differential to include Pneumocystis pneumonia, tuberculosis, and opportunistic infections, particularly if CD4+ count <200 cells/μL 1

Chronic bronchitis patients: Sudden worsening with increased sputum volume, purulence, or dyspnea suggests acute exacerbation, often triggered by viral infection with bacterial superinfection (S. pneumoniae, H. influenzae, M. catarrhalis) 1

Pertussis: Suspect in adults with cough ≥2 weeks accompanied by paroxysms, post-tussive vomiting, or inspiratory whoop 3

Critical Pitfalls to Avoid

• Never diagnose "idiopathic cough" until all common and uncommon causes have been systematically evaluated and treated 1
• Do not use nasal decongestant sprays >3-5 days due to rebound congestion risk 2
• Always treat sequentially AND additively because >50% of chronic cough cases have multiple simultaneous causes 1
• Do not stop evaluation at normal chest X-ray—proceed to CT if symptoms persist despite appropriate treatment 1
• Consider drug-induced cough from ACE inhibitors, beta-blockers, or other medications 1

Treatment Adjustments Based on Response

If partial response after 4-6 weeks: Add therapy for next most likely cause rather than abandoning current treatment 1

If no response after 8 weeks of appropriate therapy: Reclassify as refractory chronic cough and consider gabapentin/pregabalin for cough hypersensitivity syndrome 5