Nonfibrotic (cellular) hypersensitivity pneumonitis with and without slight lung distortion

Background

According to international diagnostic guidelines for hypersensitivity pneumonitis (HP), cases with both nonfibrotic and fibrotic lesions are classified by the predominant feature. Therefore, some cases with nonfibrotic HP, have inflammatory lesions alone, while others have a mixture of fibrosis and inflammation. We investigated the impact of slight fibrotic lesions in nonfibrotic HP.

Methods

This retrospective study included nonfibrotic HP cases with <10% of lung distortion on high-resolution CT. We divided the cases into two groups: those with pure ground glass opacities (GGOs) without lung distortion and those with slight lung distortion of <10%.

Results

In this study, 37 cases were included. The mean baseline forced vital capacity (FVC) was 109% in the pure GGO group and 96% in the slight lung distortion group (p = 0.038). After 1 year, the reticular shadows appeared or increased more in the slight lung distortion group than in the pure GGO group (16% vs. 8%, p = 0.030). The time to medication initiation was significantly shorter in the slight lung distortion group than in the pure GGO group (p = 0.044). %FVC decreased by ≥ 5% from diagnosis in no cases with the pure GGO and in two cases with the slight lung distortion (−11.0% for 9.5 years and −10.7% for 1.3 years, respectively).

Conclusions

The slight distortion group exhibited a higher rate of worsening and new appearance of reticular shadows after 1 year and a shorter time to first medication compared to the pure GGO group.