Interstitial lung disease

Interstitial Lung Disease
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Patient Information
Overview
Classification Fibrosis lung response Occupational lung disease Drug-induced lung injury Radiation-induced lung injury Smoking related interstitial lung disease Idiopathic interstitial pneumonia Pulmonary alveolar proteinosis Lymphocytic infiltrative disorders Pulmonary lymphangioleiomyomatosis Pulmonary hemorrhage syndromes Interstitial lung disease associated with systemic diseases Granulomatous lung response
Pathophysiology
Differentiating Interstitial Lung Disease from other Diseases
Laboratory Finidngs

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

Synonyms and keywords: Diffuse parenchymal lung disease; DPLD; ILD

Classification

Interstitial lung disease may be classified on the basis of lung response to tissue injury and include:

• Lung response: Granulomatous
• Lung response: Alveolitis, interstitial inflammation, and fibrosis

Interstitial lung disease

Lung Response: Granulomatous

Lung Response: Alveolitis, Interstitial Inflammation, and Fibrosis

Known

Idiopathic (Unknown)

Hypersensitivity pneumonitis (organic dusts)

Inorganic dusts

Sarcoidosis

Lymphomatoid granulomatosis

Granulomatous vasculitides

Bronchocentric granulomatosis

Beryllium

Silica

Eosinophilic granulomatosis with polyangiitis (Churg Strauss syndrome)

Granulomatosis with polyangiitis (Wegener)

Known cause

Idiopathic (Unknown)

Drug-induced pulmonary toxicity

Occupational and environmental exposure

Radiation-induced lung injury

Aspiration pneumonia

Smoking-related

Residual of acute respiratory distress syndrome

Inhaled inorganic dust

Inhaled organic dusts

Inhaled agents other than inorganic or organic dusts

Desquamative interstitial pneumonia

Respiratory bronchiolitis–associated interstitial lung disease

Pulmonary Langerhans cell granulomatosis

Pulmonary alveolar proteinosis

Idiopathic interstitial pneumonias

Lymphocytic infiltrative disorders (lymphocytic interstitial pneumonitis associated with connective tissue disease)

Connective tissue diseases

Gastrointestinal or liver diseases

Inherited diseases

Graft-versus-host disease

Pulmonary hemorrhage syndromes

Eosinophilic pneumonias

Lymphangioleiomyomatosis

Amyloidosis

Major idiopathic interstitial pneumonias

Rare idiopathic interstitial pneumonias

Unclassifiable idiopathic interstitial pneumonias

• Idiopathic pulmonary fibrosis • Idiopathic nonspecific interstitial pneumonia • Respiratory bronchiolitis-interstitial lung disease • Desquamative interstitial pneumonia • Cryptogenic organising pneumonia • Acute interstitial pneumonia

• Idiopathic lymphoid interstitial pneumonia • Idiopathic pleuroparenchymal fibroelastosis

• Systemic lupus erythematosus • Rheumatoid arthritis • Ankylosing spondylitis • Systemic sclerosis • Sjögren syndrome • Polymyositis • Dermatomyositis

• Crohn disease • Primary biliary cirrhosis • Chronic active hepatitis • Ulcerative colitis

• Tuberous sclerosis • Neurofibromatosis • Niemann-Pick disease • Gaucher disease • Hermansky-Pudlak syndrome

• Bone marrow transplantation • Solid organ transplantation

• Goodpasture syndrome • Idiopathic pulmonary hemosiderosis • Isolated pulmonary capillaritis

Pathophysiology

Algorithm showing pathophysiology of Interstitial Lung Disease

Tissue injury in lungs

Parenchymal injury

Vascular injury

Mast cells in lungs in response to tissue injury

LPA6, LPA2, and LPA4 receptors

Decreased sFRP-1 (secreted frizzled-related protein 1) in fibroblasts

Secretes tryptase

Transforming growth factor-β (TGF-β)

Insulin-like growth factor (IGF) signalling

Reduced expression of angiogenic factors, vascular endothelial growth factor (VEGF)

Elevation of angiostatic factors, pigment epithelium-derived factor

Wnt/β-catenin signalling pathway

PAR-2/protein kinase (PK)C-α/Raf-1/p44/42 signaling pathway

Upregulation of Egr-1 (early growth response protein 1)

IGF-binding protein 5 (IGFBP-5)

IGF-binding protein 3 (IGFBP-3)

Loss of endothelial barrier function

Dysregulation of repair in lung tissue and activation of fibroblasts

Regulates transforming growth factor-β (TGF-β)

Induction of syndecan-2 (SDC2)

Activation,proliferation, and migration of fibroblast to the site of injury

Fibroblasts

Altered PTEN (phosphatase and tensin homologue)/Akt axis

Acquire contractile stress fibres

Inactivates Fox (forkhead box) O3a

Protomyofibroblast, composed of cytoplasmic actins

Pleural mesothelial cells (PMCs)

Downregulation of caveolin-1 (cav-1) and Fas expression

De novo expression of α-smooth muscle actin (α-SMA)

TGF-β1-dependent mesothelial–mesenchymal transition

Fibroblast resistant to apoptosis

Myofibroblasts

Different ranges of contractions mediated by RhoA/Rho-associated kinase

Changes in intracellular calcium concentrations

Recruitement of fibrocytes in lungs

Lock step mechanism of cyclic and contractile events

T-helper cell type 2 on site of injury

Upregulation of C-X-C chemokine receptor type 4 (CXCR4) on fibrocytes and its ligand CXCL12 (stromal cell-derived factor 1)

Excess extracellular matrix production

Exerting traction force

Interleukin-13

Migration of fibrocytes to the site of injury

Tissue remodelling

Alternate pathway activation of macrophages

Lung Fibrosis

References

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