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Cough-Variant Asthma — RACP Adult Medicine MCQ

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ModerateRespiratoryCough-Variant AsthmaRACP Adult Medicine

A 40-year-old woman presents with a 4-month history of dry cough, particularly after exercise and exposure to cold air. She has nocturnal cough. CXR is normal. Spirometry shows normal FEV₁/FVC ratio with a positive bronchial provocation test (methacholine challenge with PC₂₀ <4 mg/mL). She is not on any medications. What is the most likely cause?

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Correct answer: D — Asthma

Chronic dry cough worse with exercise and cold air, nocturnal symptoms, and positive methacholine challenge (bronchial hyperreactivity) is cough-variant asthma. Spirometry may be normal between episodes. Methacholine challenge is the diagnostic test when spirometry is non-diagnostic. Treatment is a trial of ICS (or ICS/formoterol MART) — cough should improve within 2-4 weeks.

Reference: Australian Asthma Handbook – 2024; eTG Respiratory 2024