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Mosaic attenuation in hypersensitivity pneumonitis — SCE Respiratory MCQ

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HardImagingMosaic attenuation in hypersensitivity pneumonitisSCE Respiratory

A 48-year-old bird breeder has exertional breathlessness and cough. Inspiratory HRCT shows patchy ground-glass change, and expiratory imaging demonstrates lobular air trapping creating mosaic attenuation. BAL lymphocytes are 38% and avian precipitins are positive. Spirometry shows mild restriction with reduced TLCO. What is the most likely underlying cause?

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Correct answer: B — Small-airways involvement in hypersensitivity pneumonitis

Mosaic attenuation with expiratory air trapping indicates small-airways disease, and the exposure plus BAL lymphocytosis points to hypersensitivity pneumonitis. Pulmonary venous hypertension may cause mosaic perfusion but does not explain avian precipitins and BAL lymphocytosis. Expiratory HRCT is essential when HP is suspected.

Reference: ATS/JRS/ALAT Hypersensitivity Pneumonitis Guideline; Fleischner glossary