A 29-year-old spray painter develops cough and nocturnal wheeze that improves on weekends and holidays and worsens through the working week. Symptoms began roughly eight months after he started this job. Serial peak expiratory flow measured at work and away from work shows a diurnal variation greater than 20%. What is the most likely diagnosis?

• A Byssinosis
• B Occupational hypersensitivity pneumonitis
• C Reactive airways dysfunction syndrome
• D Occupational asthma due to isocyanates ✓

Explanation

Diisocyanates used in polyurethane paints are among the commonest causes of immunologic occupational asthma. Typical clues are work-related periodicity, improvement during absences from work, a latent interval between exposure onset and symptoms, and confirmatory serial peak flow monitoring showing more than 20% variability. Reactive airways dysfunction syndrome differs because it begins abruptly after a single massive irritant exposure with no latent period. Hypersensitivity pneumonitis produces restrictive disease and systemic symptoms rather than variable airflow obstruction.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.