What is the differential diagnosis for an adult patient with a dry cough and sore throat, without fever or cold symptoms, and potentially with a history of respiratory conditions or exposures to irritants?

Differential Diagnosis for Dry Cough with Sore Throat Without Fever or Cold

The most likely diagnosis is upper airway cough syndrome (UACS, formerly postnasal drip syndrome), followed by cough-variant asthma, gastroesophageal reflux disease (GERD), or a combination of these conditions. 1

Primary Differential Diagnoses

Upper Airway Cough Syndrome (UACS)

• UACS is the leading cause when nasal discharge, throat clearing, or postnasal drip sensation accompanies the cough, even without overt rhinorrhea or nasal congestion. 1
• The absence of fever and cold symptoms does not exclude UACS, as chronic rhinosinusitis can present with minimal nasal symptoms. 2
• Sore throat in this context typically results from chronic throat clearing and postnasal drainage irritating the pharynx. 1

Cough-Variant Asthma

• Suspect this when cough worsens at night, with cold air exposure, or with exercise. 2, 1
• Cough may be the only manifestation of asthma, occurring without wheezing or dyspnea. 2
• Normal spirometry does not exclude the diagnosis; bronchoprovocation testing may be required. 2
• The dry nature of the cough fits this diagnosis particularly well. 2

Gastroesophageal Reflux Disease (GERD)

• GERD-associated cough frequently occurs without any gastrointestinal symptoms such as heartburn or regurgitation. 2, 1
• The sore throat may represent laryngopharyngeal reflux causing posterior pharyngeal irritation. 1
• This diagnosis should be strongly considered if UACS and asthma treatments fail. 1

Secondary Considerations

ACE Inhibitor-Induced Cough

• If the patient takes an ACE inhibitor, this medication must be stopped immediately, as it causes chronic dry cough in 5-35% of patients. 1, 3
• Cough typically resolves within days to 2 weeks (median 26 days) after discontinuation. 1
• No patient with troublesome cough should continue ACE inhibitors. 2

Post-Infectious Cough

• If symptoms began 3-8 weeks ago following an acute respiratory infection, post-infectious cough is likely. 1
• This typically presents as persistent dry cough after the acute illness has otherwise resolved. 1

Environmental or Occupational Irritant Exposure

• Chronic exposure to irritants (smoke, chemicals, dust) can cause persistent dry cough without systemic symptoms. 2
• A thorough occupational history is mandatory. 2

Less Common but Important Diagnoses

Drug-Induced Cough (Beyond ACE Inhibitors)

• Beta-blockers, inhaled medications, nitrofurantoin, and mycophenolate mofetil can cause chronic dry cough. 2
• Consider any medication started within the past several months. 2

Eosinophilic Bronchitis

• Presents with chronic dry cough, normal spirometry, and no airway hyperresponsiveness. 2
• Requires sputum eosinophil count or bronchoscopy for diagnosis. 1

Early Malignancy

• While less likely without constitutional symptoms, chronic cough warrants chest radiography to exclude lung cancer or mediastinal masses. 1, 4
• This is particularly important in patients with smoking history or occupational exposures. 4

Critical Exclusions

Pneumonia

• The absence of fever, abnormal vital signs (heart rate ≥100 beats/min, respiratory rate ≥24 breaths/min, temperature ≥38°C), and focal chest findings makes pneumonia unlikely. 2
• Chest radiography is mandatory to definitively exclude this diagnosis. 2, 1

Tuberculosis

• Consider if the patient has resided in endemic areas, has HIV risk factors, or has unexplained weight loss. 2
• The absence of fever, night sweats, and weight loss makes this less likely. 1

Congestive Heart Failure

• Dry cough can be an early manifestation, but absence of dyspnea on exertion and orthopnea makes this unlikely. 2
• Chest radiography will help exclude this. 1

Common Pitfalls to Avoid

• Do not diagnose acute bronchitis in the absence of an acute viral upper respiratory infection, as this leads to inappropriate antibiotic prescribing. 2
• Do not assume purulent sputum indicates bacterial infection; it commonly occurs with viral infections due to neutrophil influx. 2, 5
• Do not overlook medication history, particularly ACE inhibitors, which are frequently missed as a cause. 1
• Do not diagnose idiopathic cough until systematic evaluation and adequate therapeutic trials of UACS, asthma, and GERD have been completed. 1

Recommended Diagnostic Approach

1. Obtain chest radiograph and spirometry immediately. 2, 1
2. Review all medications and stop any ACE inhibitors. 1, 3
3. Initiate empiric trial of first-generation antihistamine-decongestant combination for 1-2 weeks to treat presumed UACS. 1
4. If no response, proceed to asthma evaluation with bronchodilator trial or bronchoprovocation testing. 1
5. If both fail, initiate intensive GERD therapy with high-dose PPI for minimum 8-12 weeks. 1
6. Consider advanced testing (HRCT, bronchoscopy, 24-hour pH monitoring) only after adequate therapeutic trials have failed. 1