What are the differential diagnoses for a 38‑year‑old with abrupt pleuritic, positional chest pain for three days that worsens when supine, improves when sitting up, is unresponsive to acid‑suppressive therapy, and has a recent upper‑respiratory infection and a urinary endoscopic procedure one month ago?

Differential Diagnoses for Pleuritic, Positional Chest Pain in a 38-Year-Old

The most likely diagnosis is acute viral pericarditis given the pleuritic and positional nature of the pain (worse supine, better sitting up), recent upper respiratory infection, lack of response to acid suppression, and ability to exercise without limitation. 1

Life-Threatening Causes to Exclude First

Pericarditis (Most Likely)

• Sharp, pleuritic chest pain that improves when sitting forward and worsens when supine is the hallmark presentation of acute pericarditis. 2, 1
• The recent upper respiratory infection 5 days ago strongly supports a viral etiology, as viruses (Coxsackieviruses, respiratory syncytial virus, influenza, parainfluenza, adenovirus, Epstein-Barr virus) are common causative agents. 3
• Diagnosis requires pleuritic chest pain plus at least one of: pericardial friction rub on auscultation, ECG changes (PR-segment depression or diffuse concave ST-segment elevations), or new/growing pericardial effusion on echocardiography. 2
• Obtain an ECG within 10 minutes and consider transthoracic echocardiography to evaluate for pericardial effusion. 1

Pulmonary Embolism (Must Rule Out)

• PE presents with dyspnea, pleuritic chest pain, tachycardia, and tachypnea in >90% of cases and must be excluded before considering benign etiologies. 1
• The urinary surgery one month ago represents a recent surgical risk factor, though the timing makes this less likely. 1
• Critical pitfall: A normal chest X-ray does NOT exclude PE. 1
• Apply Wells criteria to determine pretest probability; if low-to-intermediate, obtain age- and sex-specific D-dimer. 1
• The ability to play pickleball without complications makes PE significantly less likely, as PE typically causes dyspnea with exertion. 1

Acute Coronary Syndrome

• Approximately 13% of ACS patients present with pleuritic-type chest pain. 1
• Critical pitfall: 7% of patients with reproducible chest wall tenderness still have ACS, so the absence of tenderness to palpation does not exclude cardiac disease. 1
• The patient's age (38), ability to exercise vigorously, and lack of radiation make ACS less likely but not impossible. 1
• Obtain cardiac troponin as soon as possible. 1

Pneumothorax

• Classic triad includes dyspnea, pleuritic pain on inspiration, and unilateral absence of breath sounds with hyperresonant percussion. 1
• The lack of dyspnea and ability to play pickleball make this unlikely. 1

Aortic Dissection

• Presents with sudden "ripping" chest or back pain radiating to the back, with pulse differential in ~30% of cases. 1
• The absence of radiation and the positional nature of this patient's pain make dissection very unlikely. 1

Common Non-Life-Threatening Causes

Viral Pleurisy/Pleurodynia

• Viruses commonly cause pleuritic chest pain following upper respiratory infections. 3
• Enterovirus epidemic myalgia (Bornholm disease) can mimic costochondritis and cause musculoskeletal chest pain. 4
• The recent viral prodrome (runny nose) and daughter's illness support this diagnosis. 3

Costochondritis

• Characterized by tenderness of costochondral joints on palpation. 1
• However, the patient reports NO tenderness to palpation, making this diagnosis less likely. 1
• Occult chest trauma or recent injury can present as costochondritis even without clear history. 4

Pneumonia

• Presents with localized pleuritic pain, fever, productive cough, regional dullness to percussion, and egophony. 1
• The absence of cough, fever, and productive sputum makes pneumonia unlikely. 1
• Important: In patients with persistent symptoms or those who smoke, document radiographic resolution with repeat chest X-ray six weeks after initial treatment. 3

Diagnostic Algorithm

Immediate Testing (First 10 Minutes)

1. Obtain 12-lead ECG to identify pericarditis patterns (diffuse ST-elevation with PR-depression), STEMI, or PE-related changes. 1
2. Obtain PA and lateral chest radiograph to screen for pneumothorax, pneumonia, pleural effusion, or mediastinal widening. 1
3. Measure cardiac troponin to exclude myocardial injury. 1

Risk Stratification

• Apply Wells criteria for PE given the recent surgical history. 1
• If low-to-intermediate probability, obtain D-dimer with age- and sex-specific cutoffs. 1
• If high probability or positive D-dimer, proceed to CT pulmonary angiography. 1

If Initial Testing Suggests Pericarditis

• Obtain transthoracic echocardiography to determine presence of pericardial effusion, ventricular wall motion abnormalities, or restrictive physiology. 1
• Consider cardiac MRI with gadolinium if diagnostic uncertainty exists or to determine extent of pericardial inflammation. 1

Management Based on Diagnosis

If Pericarditis is Confirmed

• Acetaminophen can be given for symptomatic relief in early pericarditis. 2
• If symptoms persist, high-dose aspirin (500-1,000 mg every 6-8 hours) may be used to reduce symptoms. 2
• Consider colchicine (0.5-0.6 mg once or twice daily for 3 months) to reduce symptoms and decrease risk of recurrence. 2
• Daily dosing of colchicine should be used in patients who weigh <70 kg. 2
• Critical warning: Glucocorticoids and NSAIDs (other than aspirin) are potentially harmful due to possible increased risk of recurrent MI or impaired myocardial healing. 2

If Viral Pleurisy/Costochondritis

• NSAIDs are appropriate for pain management in those with virally triggered or nonspecific pleuritic chest pain. 3
• Provide reassurance and thorough explanation of the benign nature if cardiac testing is negative. 1

Red Flags Requiring Immediate ED Transfer

• Any concern for ACS, PE, pneumothorax, or aortic dissection should prompt immediate EMS transport to the emergency department. 1
• Development of dyspnea, hemodynamic instability, or syncope. 1