Hypersensitivity Pneumonitis

Dr. Carvalho presented a case of a middle aged woman with a history of chronic hypoxia, obesity, asthma and PFTs with restrictive physiology who presented with progressive dyspnea with exertion. Her chest CT is shown below.


How would you describe the findings on CT?

Hard question huh? Luckily Dr. Molly Downey, a PGY-3 in radiology was there to save the day.

The following slides are all from Molly’s talk. Many of the images are from Radiology Assistant and Radiopaedia which are great resources for imaging pearls and differentials.

Screen Shot 2019-09-25 at 10.42.57 PM.png
Screen Shot 2019-09-25 at 10.19.52 PM.png
Screen Shot 2019-09-25 at 10.44.08 PM.png
Screen Shot 2019-09-25 at 10.20.51 PM.png

The patient’s imaging findings were highly suspicious for hypersensitivity pneumonitis.

What ROS and exposure questions would you ask a patient with these imaging findings?

The list of identified antigens is extensive. Our approach is to start with a ROS similar to what’s shown below, and then dig deeper if any of these histories are positive.

What Medication exposure would you explicitly ask about?

there are a lot (see UpToDate chart below). The top three we think of are:

  1. amiodarone

  2. methotrexate

  3. chemotherapies

Interestingly, her extensive pulmonary review of systems revealed that she had a very strong history of inhaling popcorn and this was thought to be a possible antigen.


The patient ultimately underwent a lung biopsy which interesting did not show microscopic evidence of hypersensitivity pneumonitis but more so chronic aspiration (thought historicallyt would not be so diffuse on imaging) raising concern for false result, or need for upper lobe biopsies. She had symptomatic improvement with burst of steroids raising even more concern for a clinical picture more convincing of HP despite negative biopsies .

An essential part of treatment of HP is avoidance of the antigen though this doesn’t appear to improve long term outcomes. According to an older small prospective study, patients that received steroids for HP had improved symptoms and minor improvements DLCO initially but at 5 years there was no improvement in DLCO, FEV1, FVC. (1) Another study showed no difference in lung function or working capacity but did find that patients who received steroids had reduced fibrosis on CT. (2) It also showed that longer steroid doses (12 weeks) had no advantage over shorter courses (4 weeks).


(1) Kokkarinen JI1, Tukiainen HO, Terho EO. Effect of corticosteroid treatment on the recovery of pulmonary function in farmer's lung. Am Rev Respir Dis. 1992;145(1):3.

(2) Mönkäre S. Influence of corticosteroid treatment on the course of farmer's lung. Eur J Respir Dis. 1983, May;64(4):283-93.