Acute Exacerbation and Proposed Criteria for Progressive Pulmonary Fibrosis in Patients with Fibrotic Hypersensitivity Pneumonitis and Idiopathic Pulmonary Fibrosis

BACKGROUND

Acute exacerbation (AE) occasionally develops in the course of fibrotic hypersensitivity pneumonitis (HP).

OBJECTIVE

The aim of the study was to compare AE of fibrotic HP with that of idiopathic pulmonary fibrosis (IPF).

METHODS

Consecutive patients with pathologically confirmed fibrotic HP and IPF diagnosed based on a multidisciplinary discussion were included in the analysis. AE in patients with fibrotic HP and IPF was evaluated retrospectively.

RESULTS

This study included 309 and 160 patients with fibrotic HP and IPF, respectively. Their 50% survival times were 96.1 and 78.0 months, respectively (hazard ratio [HR]: 0.54 [95% confidence interval, CI: 0.36-0.77], log-rank test; p < 0.001). Notably, the cumulative AE rates of fibrotic HP were 3% at 1 year and 10% at 3 years. Moreover, the corresponding rates of IPF were 8% at 1 year and 20% at 3 years (HR: 0.66 [95% CI: 0.45-0.93], log-rank test; p = 0.034). The 90-day survival rates from the AE onset of fibrotic HP and IPF were 75% and 64%, respectively (HR: 0.51 [95% CI: 0.31-0.83], log-rank test; p = 0.006). The respiratory function test on the physiological criteria of progressive pulmonary fibrosis (PPF) was a predictor of AE in fibrotic HP. However, the high-resolution CT (HRCT) changes in the criteria of PPF were not. Nevertheless, both the physiological and radiological criteria of PPF were a predictor of AE of IPF.

CONCLUSION

AE of fibrotic HP has a lesser prognostic effect than that of IPF. HRCT criteria for PPF were not a risk factor for AE in patients with fibrotic HP.

Serum Immunoglobulin G Testing against Pigeon Egg in Stable Fibrotic Hypersensitivity Pneumonitis

INTRODUCTION

The accuracy of serum immunoglobulin (Ig) G testing for diagnosis of stable bird-related fibrotic hypersensitivity pneumonitis (HP) is controversial. Furthermore, avian serum, extracts, or feathers were employed as antigens in bird-related HP; however, the usage of egg whites has not been reported. We investigated the utility of IgG testing against pigeon egg whites in patients with stable bird-related fibrotic HP.

METHODS

Patients having a positive inhalation test for pigeon antigen and a histological investigation with diagnostic confidence of fibrotic HP greater than moderate confidence were included. The control group consisted of patients with interstitial lung diseases (ILDs) other than HP. To select patients in the stable phase, patients with fibrotic HP were excluded if they were clinically considered to be in the acute exacerbation or acute phase. The IgG testing against pigeon egg whites by enzyme-linked immunosorbent assay and the commercialized anti-pigeon IgG testing by fluorescence enzyme immunoassay were investigated.

RESULTS

In this study, 37 patients with stable bird-related fibrotic HP and 32 patients with ILDs other than HP participated. Serum IgG testing for pigeon egg whites revealed that the control group's optical density was 0.147 and the group with bird-related fibrotic HP had a mean value of 0.207 (p = 0.011). IgG testing in bronchial alveolar lavage fluid was not significantly higher in the bird-related fibrotic HP group than in controls (p = 0.42). No significant difference in area under the curve between an IgG testing against pigeon egg whites and a commercialized anti-pigeon IgG testing was observed (p = 0.24). Test accuracy for stable bird-related fibrotic HP ranged from 62% to 76% sensitivity and 59-66% specificity.

CONCLUSION

IgG testing to identify the inciting antigen in patients with stable bird-related fibrotic HP had relatively low accuracy.

Novel acute hypersensitivity pneumonitis model induced by airway mycosis and high dose lipopolysaccharide

BACKGROUND

Inhalation of fungal spores is a strong risk factor for severe asthma and experimentally leads to development of airway mycosis and asthma-like disease in mice. However, in addition to fungal spores, humans are simultaneously exposed to other inflammatory agents such as lipopolysaccharide (LPS), with uncertain relevance to disease expression. To determine how high dose inhalation of LPS influences the expression of allergic airway disease induced by the allergenic mold Aspergillus niger (A. niger).

METHODS

C57BL/6J mice were intranasally challenged with the viable spores of A. niger with and without 1 μg of LPS over two weeks. Changes in airway hyperreactivity, airway and lung inflammatory cell recruitment, antigen-specific immunoglobulins, and histopathology were determined.

RESULTS

In comparison to mice challenged only with A. niger, addition of LPS (1 μg) to A. niger abrogated airway hyperresponsiveness and strongly attenuated airway eosinophilia, PAS+ goblet cells and TH2 responses while enhancing TH1 and TH17 cell recruitment to lung. Addition of LPS resulted in more severe, diffuse lung inflammation with scattered, loosely-formed parenchymal granulomas, but failed to alter fungus-induced IgE and IgG antibodies.

CONCLUSIONS

In contrast to the strongly allergic lung phenotype induced by fungal spores alone, addition of a relatively high dose of LPS abrogates asthma-like features, replacing them with a phenotype more consistent with acute hypersensitivity pneumonitis (HP). These findings extend the already established link between airway mycosis and asthma to HP and describe a robust model for further dissecting the pathophysiology of HP.