What is the most likely diagnosis and first‑line treatment for a patient with a five‑month history of chest wall pain that is reproducible on palpation and lacks red‑flag features such as exertional dyspnea, syncope, diaphoresis, radiation to the jaw or arm, abnormal vital signs, abnormal electrocardiogram, or elevated troponin?

Costochondritis: Most Likely Diagnosis and First-Line Treatment

The most likely diagnosis is costochondritis, and first-line treatment consists of NSAIDs (ibuprofen 400–600 mg three times daily or naproxen 500 mg twice daily) combined with reassurance after cardiac causes have been excluded.

Diagnostic Reasoning

Why Costochondritis Is Most Likely

• Chest wall pain reproducible on palpation is the defining feature of costochondritis and accounts for approximately 43% of chest-pain presentations in primary care after cardiac causes are excluded. 1
• Five-month duration indicates a chronic, stable pattern inconsistent with acute life-threatening conditions such as acute coronary syndrome, aortic dissection, or pulmonary embolism. 2
• Absence of red-flag features—no exertional dyspnea, syncope, diaphoresis, radiation to jaw or arm, abnormal vital signs, normal ECG, and normal troponin—effectively rules out acute coronary syndrome and other emergent cardiac diagnoses. 2, 1

Critical Caveat: Reproducible Tenderness Does Not Fully Exclude Cardiac Disease

• Up to 7% of patients with chest-wall tenderness on palpation still have acute coronary syndrome, so reproducible pain alone cannot definitively exclude cardiac ischemia without objective testing. 1
• The American College of Cardiology mandates a 12-lead ECG within 10 minutes and immediate high-sensitivity troponin measurement in any patient with chest pain to rule out myocardial injury, even when musculoskeletal pain appears likely. 1, 3
• A normal ECG and two negative serial troponin measurements (at presentation and 6–12 hours after symptom onset) are required to confidently exclude acute coronary syndrome before attributing symptoms to a benign musculoskeletal cause. 1, 3

First-Line Treatment for Costochondritis

Pharmacologic Management

• NSAIDs are the cornerstone of therapy: ibuprofen 400–600 mg orally three times daily or naproxen 500 mg orally twice daily for 1–2 weeks. 1
• Acetaminophen 500–1000 mg every 6 hours may be used as an alternative in patients with contraindications to NSAIDs (e.g., peptic ulcer disease, chronic kidney disease, anticoagulation). 4

Non-Pharmacologic Measures

• Reassurance that the condition is benign and self-limited is essential to reduce anxiety and prevent unnecessary repeat evaluations. 4
• Activity modification: avoid movements that exacerbate pain (e.g., heavy lifting, repetitive twisting, deep breathing exercises that provoke discomfort). 4
• Local heat application may provide symptomatic relief. 4

When to Escalate Treatment

• If symptoms persist beyond 2–3 weeks despite NSAIDs, consider a short course of oral corticosteroids (e.g., prednisone 20–40 mg daily for 5–7 days) or referral for local corticosteroid injection into the costochondral junction. 1
• Physical therapy with stretching and postural exercises may be beneficial for refractory cases. 4

Algorithmic Approach to Chronic Chest-Wall Pain

1. Obtain a 12-lead ECG and high-sensitivity troponin to exclude acute coronary syndrome, even when the presentation strongly suggests musculoskeletal pain. 1, 3
2. If ECG and troponin are normal, perform a focused physical examination to reproduce the pain by palpating the costochondral junctions, sternum, and chest wall. 1, 4
3. If pain is reproducible and no red-flag features are present, diagnose costochondritis and initiate NSAID therapy with reassurance. 1, 4
4. If pain is not reproducible or red-flag features emerge (e.g., new dyspnea, syncope, radiation to jaw/arm), proceed with further cardiac evaluation including stress testing or coronary CT angiography. 2, 1, 3
5. Arrange follow-up within 1–2 weeks to reassess symptom response and ensure no evolution of concerning features. 4

Common Pitfalls to Avoid

• Do not assume reproducible chest-wall tenderness fully excludes cardiac disease; 7% of such patients have acute coronary syndrome. 1
• Do not delay ECG and troponin testing in any patient with chest pain, regardless of how "typical" the musculoskeletal features appear. 1, 3
• Avoid the term "atypical chest pain"; instead describe the presentation as "non-cardiac" after objective testing confirms the absence of ischemia. 2, 1
• Do not prescribe opioids for costochondritis; NSAIDs and reassurance are sufficient for the vast majority of patients. 4