A 24-year-old patient presents with sudden onset chest pain. The patient is tall and thin, physically active, and breath sounds are diminished on the right. Which condition should be suspected?

• A. Spontaneous pneumothorax
• B. Hyperventilation syndrome
• C. Pulmonary embolism
• D. Pleurisy

Answer: (A)

The key idea is spontaneous rupture of an apical bleb causing air to leak into the pleural space, leading to collapse of part of the lung on the affected side. In a tall, thin, young adult who experiences sudden chest pain, this pattern is classic. When air accumulates in the pleural space, the lung can collapse and breath sounds become diminished on that side, matching the clinical finding described.

Hyperventilation syndrome usually shows rapid breathing with anxiety and a relatively normal lung exam, not a unilateral reduction in breath sounds. Pulmonary embolism can cause sudden chest pain and dyspnea but lung auscultation is typically normal unless there’s an accompanying complication; diminished breath sounds on one side is not characteristic. Pleurisy causes sharp chest pain with deep breaths, but breath sounds are usually preserved unless an associated effusion or other complication is present.

So the presentation fits best with a primary spontaneous pneumothorax.