What is the differential diagnosis for a patient presenting with chest pain and a rash?

Differential Diagnosis for Chest Pain with Rash

Herpes zoster is the primary diagnosis to consider when chest pain presents with a rash, characterized by pain in a dermatomal distribution triggered by touch with a characteristic unilateral dermatomal rash. 1

Life-Threatening Causes to Exclude First

Even with a rash present, you must systematically exclude emergent cardiac and pulmonary causes before attributing symptoms solely to dermatologic pathology:

Cardiovascular Emergencies

• Acute coronary syndrome (ACS) may present with diaphoresis that could be mistaken for skin changes, along with tachycardia, tachypnea, hypotension, crackles, S3, or mitral regurgitation murmur (though examination may be normal in uncomplicated cases) 1
• Pericarditis presents with fever, pleuritic chest pain that increases in supine position and improves sitting forward, and may be associated with a friction rub 1
• Myocarditis causes fever, chest pain, heart failure signs, and S3 gallop 1
• Aortic dissection presents with sudden onset severe "ripping" chest pain radiating to the back, with extremity pulse differential in 30% of cases 1

Pulmonary Emergencies

• Pulmonary embolism presents with tachycardia and dyspnea in >90% of patients, with pleuritic pain on inspiration 1
• Pneumothorax causes dyspnea, pleuritic pain on inspiration, and unilateral absence of breath sounds with hyperresonant percussion 1
• Pneumonia presents with localized pleuritic pain, fever, productive cough, regional dullness to percussion, egophony, and possible friction rub 1

Primary Dermatologic Cause with Chest Pain

Herpes Zoster (Shingles)

This is the classic presentation of chest pain with rash in a dermatomal distribution:

• Pain in a dermatomal distribution that is triggered by touch 1
• Characteristic unilateral rash following a dermatomal pattern 1
• Pain often precedes the rash by several days, which can initially mislead clinicians toward cardiac causes 2
• The rash is vesicular and does not cross the midline 2

Critical Diagnostic Approach

Immediate Actions

1. Perform focused cardiovascular examination to identify life-threatening causes including ACS, aortic dissection, PE, or esophageal rupture 1
2. Obtain ECG within 10 minutes of presentation to identify STEMI, pericarditis patterns, or signs of pulmonary embolism 2
3. Obtain chest radiography to evaluate for pneumothorax, pneumonia, pleural effusion, or widened mediastinum 2
4. Measure cardiac troponin as soon as possible in acute presentations to exclude myocardial injury 2

Physical Examination Pearls

• Examine the rash carefully: Unilateral dermatomal distribution strongly suggests herpes zoster 1
• Assess vital signs: Tachycardia and tachypnea are present in >90% of pulmonary embolism cases 2
• Palpate chest wall: Tenderness of costochondral joints suggests costochondritis, but 7% of patients with reproducible chest wall pain still have ACS 2
• Auscultate carefully: Listen for friction rubs (pericarditis, pneumonia), absent breath sounds (pneumothorax), or cardiac murmurs 1

Common Pitfalls to Avoid

• Do not assume dermatomal rash excludes cardiac pathology: Patients can have concurrent herpes zoster and myocardial infarction, particularly in elderly or immunocompromised patients 1
• Do not rely on chest wall tenderness alone: 7% of patients with reproducible chest wall tenderness have acute coronary syndrome 2
• Do not use nitroglycerin response as a diagnostic criterion: Relief with nitroglycerin does not confirm or exclude myocardial ischemia 2
• Sharp, pleuritic pain does not exclude cardiac ischemia: 13% of patients with pleuritic pain may have acute myocardial ischemia 2, 3

Disposition Based on Findings

• If herpes zoster is confirmed with normal cardiac workup: Discharge with antiviral therapy (if within 72 hours of rash onset) and pain management 1
• If any concern for ACS or other life-threatening cause: Activate 9-1-1 for transport to ED by EMS, do not delay for additional testing in office settings 1
• If examination or testing suggests cardiac or pulmonary emergency: Admit for further evaluation and management per appropriate protocols 1