The Analysis of Surgical Lung Biopsy and Explanted Lung Specimens Sheds Light on the Pathological Progression of Chronic Bird-related Hypersensitivity Pneumonitis

Abstract

Chronic hypersensitivity pneumonitis is an interstitial pneumonia caused by an immunological reaction to the chronic inhalation of an antigen. Little is known, however, about the pathological change of the pulmonary lesions. A 33-year-old man was diagnosed with chronic bird-related hypersensitivity pneumonitis based on the findings of a surgical lung biopsy and an inhalation provocation test. He underwent lung transplantation at 8 years after the diagnosis because of disease progression. We conclude that the analysis of the explant suggests that the presence of extensive fibrosis in the centrilobular and perilobular area with bridging fibrosis is a form of pathological progression of chronic hypersensitivity pneumonitis.

Keywords: bridging fibrosis; centrilobular fibrosis; chronic hypersensitivity pneumonitis; lung transplantation; subpleural and paraseptal fibrosis.

Figure 1.

The radiological findings. A chest X-ray film shows bilateral ground glass opacities (A) and chest CT shows diffuse nodular shadow (B) in all lobes at 33 years of age. A chest X-ray film shows the progression of ground glass opacities and a decrease of lung volume capacity (C); chest CT shows a thickened interlobular septa (D) at 41 years of age.

Figure 2.

(A-C) Microscopic findings of surgical lung biopsy specimen. Centrilobular fibrosis (black arrows), subpleural and paraseptal fibrosis (black arrowheads) [A: panoramic view of the right S², Hematoxylin and Eosin (H&E) staining, ×40], bridging fibrosis (white arrows) (B: a square of A, elastica van Gieson staining, ×100) and loose granuloma (white arrowheads) (C: H&E staining, ×400) are seen. (D-H) Macroscopic and microscopic findings of the left lung explant. An irregular, convex, hard, pleural surface with a roughness of 3-5 mm and bullous change of the upper lobe are seen (D). UIP-like features are remarkable. Hyperplasia of the smooth muscle cells and progression of fibrosis are seen in the centrilobular areas (black arrows). The progression of subplerural and paraseptal fibrosis is seen; the pleura has a rough surface (black arrowheads) (E: H&E staining, ×40). The progression of thick bridging fibrosis is seen (white arrows) (F: elastica van Gieson staining, ×40). A cystic lesion with collagen deposition (black arrow) is seen (G: elastica van Gieson staining, ×200). Extensive bronchiolar metaplasia with mucus in the lower lobe are seen (white arrows) [H: elastic van Gieson staining, ×40 and ×200 (inset)].

Figure 3.

The clinical course up to lung transplantation. VC: vital capacity

Figure 4.

Comparison between the microscopy findings of a surgical lung biopsy from Rt. S⁶ (A) and the Lt. S⁶ from explant (B). The progression of bridging fibrosis shortens the distance between the centrilobular areas or between the centrilobular areas and the perilobular or subpleural areas, and results in alveolar collapse.