Question

A 29 year old anxious lady presents with progressive breathlessness and exercise intolerance for four months. Her FVC is 90% and FEV1/FVC is 86%. Oxygen saturation after exercise dropped from 92% to 86%. What is the likely diagnosis?

• A. Primary alveolar hypoventilation
• B. Primary pulmonary hypertension
• C. Anxiety disorder
• D. Interstitial lung disease

Hint:

Normal spirometry but exertional desaturation in a young woman points to the lung vessels.

Answer 1

The Correct Option is B

Step 1: Identify the pattern. A young woman has progressive breathlessness, poor exercise tolerance, and oxygen desaturation on exertion. We must explain breathlessness with normal lung mechanics.

Step 2: Read the spirometry. FVC is 90% (normal) and FEV1/FVC is 86% (normal, above 70%). So there is no obstruction and no restriction. The lungs move air normally, which rules out the usual airway or lung volume diseases.

Step 3: Look at the gas exchange clue. Resting saturation is only 92% and it falls to 86% with exercise. Exertional desaturation with normal spirometry points to a problem in the pulmonary vessels or in gas transfer, not in the airways.

Step 4: Match the diagnosis. Primary (idiopathic) pulmonary hypertension classically strikes young women, causes progressive dyspnea and exercise intolerance, and shows exertional desaturation with essentially normal spirometry. So option B fits best.

Step 5: Why the others are wrong. Interstitial lung disease would give a restrictive pattern with low FVC, but FVC is normal here (option D wrong). Primary alveolar hypoventilation causes chronic CO2 retention and is not the typical picture in a young anxious woman with normal spirometry (option A wrong). Anxiety disorder does not cause true exertional oxygen desaturation; the falling SpO2 proves an organic vascular cause (option C wrong).

Answer: B. Primary pulmonary hypertension.