Which of the following is a must-not-miss differential diagnosis for acute dyspnea?

• A. Tension pneumothorax
• B. Chronic fatigue syndrome
• C. Seasonal allergies
• D. Sarcoidosis

Answer: (A)

Evaluating acute dyspnea requires focusing on life-threatening emergencies that need immediate action. Tension pneumothorax fits this because air trapped under pressure in the pleural space collapses the lung and shifts the mediastinum, impairing venous return and risking rapid cardiovascular collapse. Clinically, it may present with sudden dyspnea, chest pain, diminished or absent breath sounds on one side, a hyperresonant chest, and distended neck veins; hypotension can develop as it worsens. In unstable patients, the priority is immediate needle decompression followed by chest tube placement, even before imaging if necessary. This urgency is why tension pneumothorax is the must-not-miss differential for acute dyspnea.

The other options don’t typically present as immediate life-threatening etiologies of acute dyspnea. Chronic fatigue syndrome is a long-term condition characterized by fatigue rather than an acute respiratory crisis. Seasonal allergies can cause breathing symptoms but are usually not an emergent cause of sudden respiratory collapse. Sarcoidosis is a chronic inflammatory disease that can involve the lungs but does not commonly present as an abrupt, life-threatening dyspnea on first presentation.