Hamman-Rich syndrome pathophysiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:

Overview

The exact pathogenesis of [disease name] is not fully understood.

OR

It is thought that [disease name] is the result of / is mediated by / is produced by / is caused by either [hypothesis 1], [hypothesis 2], or [hypothesis 3].

OR

[Pathogen name] is usually transmitted via the [transmission route] route to the human host.

OR

Following transmission/ingestion, the [pathogen] uses the [entry site] to invade the [cell name] cell.

OR

[Disease or malignancy name] arises from [cell name]s, which are [cell type] cells that are normally involved in [function of cells].

OR

The progression to [disease name] usually involves the [molecular pathway].

OR

The pathophysiology of [disease/malignancy] depends on the histological subtype.

Pathophysiology

Pathogenesis

• The exact pathogenesis of [disease name] is not fully understood.

OR

• It is understood that [disease name] is the result of / is mediated by / is produced by / is caused by either [hypothesis 1], [hypothesis 2], or [hypothesis 3].
• [Pathogen name] is usually transmitted via the [transmission route] route to the human host.
• Following transmission/ingestion, the [pathogen] uses the [entry site] to invade the [cell name] cell.
• [Disease or malignancy name] arises from [cell name]s, which are [cell type] cells that are normally involved in [function of cells].
• The progression to [disease name] usually involves the [molecular pathway].
• The pathophysiology of [disease/malignancy] depends on the histological subtype.

Genetics

• [Disease name] is transmitted in [mode of genetic transmission] pattern.
• Genes involved in the pathogenesis of [disease name] include [gene1], [gene2], and [gene3].
• The development of [disease name] is the result of multiple genetic mutations.

Gross Pathology

• Patients with acute interstitial pneumonitis, gross appearance of lungs is identical to the patients with ARDS.
• The gross appearance of lungs correlates with the stage of the diffuse alveolar damage.
  • In the early phase, the lungs are firm, boggy, and have a dark red or beefy appearance.
  • In later phases, the lungs are extremely heavy due to edema and show irregular areas of dense consolidation and fibrosis.
  • As the fibrosis progresses, cobblestoning of the pleural surface may occur.
  • Formation of peripheral cysts and honeycombing may suggest the possibility of underlying chronic fibrotic lung disease.

Microscopic Pathology

• On microscopic histopathological analysis, Acute interstitial pneumonitis will show following features:
  • Diffuse alveolar damage
  • Hyaline membrane formation
  • Interstitial fibrosis:
    • It is diffuse, uniform temporally with extensive fibroblastic and myofibroblastic proliferation and relatively less collagen deposition.
    • The uniformity of the fibroblastic/myofibroblastic proliferation and prominent activity distinguish AIP from the other types of idiopathic interstitial pneumonia.
  • Type II pneumocyte hyperplasia with cytologic atypia and bronchiolar squamous metaplasia is present.
  • Thickening and distortion of alveolar septa caused by spindle cell proliferation.
  • Intraluminal polypoid plugs formation
  • Organizing thrombi in small and medium-sized arteries
  • Biopsies taken in the later course of the disease show:
    • Enlarged and remodeled airspaces that resemble honeycomb change of UIP (usual interstitial fibrosis), but extensive fibroblastic/ myofibroblastic proliferation and collagen deposition is still present within the walls of the alveoli.