An 18-year-old man with no significant past medical history presents to the emergency department (ED) complaining of a sudden onset of chest pain that awakened him from sleep at 4 AM. The pain is located in the midsubsternal region and radiates to the neck. The patient describes it as a sharp pain; when asked to rate the pain on a scale of increasing severity from 1 to 10, he states that it is an 8. The pain worsens with inspiration and is associated with shortness of breath. The patient denies having any fevers, chills, cough, hemoptysis, nausea, or vomiting. He has not had any recent trauma or surgeries. The patient has an 8 pack-year history of smoking cigarettes. He admits to occasional marijuana use and remote experimentation with inhaled methamphetamines. He denies any alcohol use. He states that he is not currently taking any medications and does not have any known allergies to medications.

On physical examination, he is noted to be a well-developed, well-nourished male in no acute distress. He does not appear to be tachypneic or cyanotic. The vital signs show a temperature of 98.1°F (36.7°C), a blood pressure of 94/58 mm Hg, a heart rate of 67 bpm, a respiratory rate of 20 breaths/min, and an oxygen saturation of 95% while breathing room air. No jugular venous distention is noted, and the patient has a normal respiratory effort. The lungs are clear to auscultation bilaterally, without any wheezes, rales, or rhonchi. The heart examination reveals a regular rate and rhythm, with normal S1 and S2 heart sounds and no murmurs, rubs, or gallops. The abdomen is soft, nontender, and nondistended. His extremities do not exhibit any clubbing, cyanosis, or edema. No subcutaneous crepitus is appreciated on examination of the skin.

The initial laboratory findings show a white blood cell (WBC) count of 11.0 × 103/μL (11.0 × 109/L; normal range, 3.8-10.9 × 103/μL), with neutrophils at 73.9% (0.73; normal range, 41.8%-77%), a hemoglobin of 15.1 g/dL (9.37 mmol/L; normal range, 13.6-17.3 g/dL), a hematocrit of 44.0% (0.44; normal range, 39.8-50.7%), and platelets of 263 × 103/μL (263 × 109/L; normal range, 141-401 × 103/μL). The basic metabolic panel is normal. A urine toxicology screen is negative. The erythrocyte sedimentation rate (ESR) is 5 mm/hr (normal range, <15 mm/hr). An electrocardiogram (ECG) is obtained (not available), which shows a normal sinus rhythm with a heart rate of 55 bpm and no ST-segment or T-wave abnormalities. Plain chest radiographs are obtained (see Figures 1a and 1b).