Interstitial Lung Disease Flashcards
Interstitial Lung Disease
- Large group of disorders that affect the alveolar wall that ultimately lead to diffuse scarring or fibrosis
- Misnomer: Interstitial lung disease affects all components of the alveolar wall which include epithelial cells, endothelial cells, and the interstitium
Interstitial lung disease
Clinical Manifestations
- Clinical Manifestations
- Dyspnea, noticed initially on exertion
- Nonproductive cough
- Crackles prominent at lung bases
- Clubbing may be present
Interstitial lung disease
Pathophysiology
- Pathophysiology
- Decreased compliance (increased stiffness) of lungs
- Decreased lung volumes
- Loss of alveolar-capillary surface area resulting in impaired measured diffusion
- Abnormalities in small airway function without generalized airflow obstruction
- Hypoxemia without CO2 retention
- Pulmonary hypertension
Interstitial lung disease
Imaging
- Chest x-ray
- Reticular – increased linear markings
- Reticulonodular – increased linear and small nodular markings
- 10% have normal radiographic findings
- High-resolution computed tomography (HRCT)
- Can distinguish inflammation from fibrosis
- Picks up early changes
- Specific pattern may be suggestive of a particular diagnosis
Interstitial lung disease
Testing
- Tissue specimens for diagnosis
- Thorascopic lung biopsy
- Transbronchial biopsy via flexible bronchoscopy
- Bronchoalveolar lavage
- PFT
- Restrictive pattern
- Decreased lung volumes
- hypoxia
Interstitial Lung Disease
Classification
- Classification
- Known Etiology ~ 35%
- Inhaled inorganic dusts (pneumoconiosis such as asbestosis or silicosis)
- Organic antigens ( hypersensitivity pneumonitis)
- Known Etiology ~ 35%
- Unknown Etiology ~65%
- Idiopathic interstitial pneumonias
- Connective tissue diseases (rheumatic disease)
- Sarcoidosis
Interstitial Lung Disease
Unknown Etiology – continued
- Unknown Etiology – continued
- Less Common
- Pulmonary Langerhans cell histiocytosis
- Lymphangioleiomyomatosis
- Goodpasture’s Syndrome
- Wegener’s granulmomatosis
- Chronic eosinophilic pneumonia
- Pulmonary alveolar proteinosis
- Less Common
Interstitial Lung Disease
Pathologic Process
- Pathologic Processes
- 1) inflammatory process in the alveolar spaces – alveolitis
- 2) scarring – fibrosis
- Both processes often occur simultaneously
- Granuloma : localized collection of cells called epithelioid histocytes (phagocytic or macrophage), generally accompanied by T-lymphocytes, multinucleated giant cells. Noncaseating in interstitial lung diseases. Examples include hypersensitivity pneumonitis and sarcoidosis
Idiopathic Interstitial Pneumonias
- Usual interstitial pneumonia
- Desquamative interstitial pneumonia
- Respiratory bronchiolitis interstitial lung disease
- Nonspecific interstitial pneumonia
- Acute interstitial pneumonia
- Cryptogenic organizing pneumonia
- Lymphocytic interstitial pneumonia
Usual interstitial pneumonia
- Patchy areas of parenchymal fibrosis and interstitial inflammation interspersed between areas of relatively preserved lung tissue
- Fibrosis is the most prominent component of the pathology
- Honeycombing – cystic airspace from retraction of surrounding fibrotic tissue
- Most important disorder in this category is idiopathic pulmonary fibrosis
Desquamative interstitial pneumonia
- More homogenous than UIP
- Large number of intraalveolar mononuclear cells
- Less prominent inflammation and little associated fibrosis
- Uniform process
- Minimal architectural distortion
- Pigmented macrophages in respiratory bronchioles secondary to smoking
- Smoking is believed to be an important underlying cause
Respiratory bronchiolitis interstitial lung disease
- Related to DIP
- Associated with pigmented macrophages which are present within the lumen of respiratory bronchioles
- Interstitial inflammation is not present
- Almost always associated with smoking
- Most important intervention is smoking cessation
Nonspecific interstitial pneumonia
- Mononuculear cell infiltration within the alveolar walls
- Uniform process
- Fibrosis is variable, but less than UIP
- Idiopathic or connective tissue disorder
- Better prognosis
Acute interstitial pneumonia
- Organizing or fibrotic stage of alveolar damage, which is the histologic pattern seen in ARDS.
- No initial trigger identified.
- Histology shows fibroblast proliferation and type II pneumocyte hyperplasia in the setting of what appears to be organizing alveolar damage
Cryptogenic organizing pneumonia
- Organizing fibrosis (granulation tissue) in small airways
- Mild degree of chronic interstitial inflammation
- Intraluminal airway involvement is a key feature
- Idiopathic
- Differential: infections, toxic inhalants, or connective tissue disease
Idiopathic pulmonary fibrosis
- No recognizable inciting agent
- Dysregulated pattern of fibrosis in response to alveolar epithelial injury
- Presents between ages 50-70
- Insidious onset
- Dyspnea is the most common complaint
- Rales on lung examination
- Patients frequently have clubbing
Idiopathic pulmonary fibrosis
Imaging
- Chest x-ray
- Interstitial pattern that is generally bilateral and relatively diffuse
- More prominent at lung bases, particularly in the peripheral subpleural regions
- High Resolution CT
- Interstitial densities that are patchy, peripheral, subpleural, and associated with small cystic spaces.
- Honeycombing – indicated irreversible fibrosis
Idiopathic pulmonary fibrosis
Dx & Px
- Diagnosis made with surgical lung biopsy
- HRCT with classic pattern of honeycombing – diagnostic in patient too frail for lung biopsy
- Prognosis
- Poor with mean survival at time of diagnosis 2-5 years
- No proven effective treatment
Desquamative interstitial pneumonia
- Smokers
- Subacute
- Ground glass appearance on imaging
- Lung biopsy with a uniform accumulation of intraalveolar macrophages with little or no fibrosis
- Prognosis better than IPF
- Improves with smoking cessation and may respond to corticosteroids
Nonspecific interstitial pneumonia
- Nonspecific interstitial pneumonia
- Ground glass appearance on imaging – inflammation
- Lung biopsy with predominantly inflammatory response in the alveolar walls , with little fibrosis
- Prognosis depends on degree of fibrosis
- Patients often respond to corticosteroids
Cryptogenic organizing pneumonia
- Connective tissue plug in small airway accompanied by mononuclear cell infiltration of the surrounding lung parenchyma
- Large majority have no specific cause
- Chest x-ray often mimics pneumonia with one or more alveolar infiltrates
- Subacute presentation over weeks to months with constitutional as well as respiratory symptoms
- Response to steroid is dramatic and occurs over days to weeks.
- Therapy is usually prolonged for months to prevent relapse
Acute Interstitial Pneumonia
- Acute disease that begins with the clinical picture of ARDS but without any usual inciting causes
- Imaging with ground glass appearance, alveolar filling
- Histology of diffuse alveolar damage, often showing some organization and fibrosis
- Mortality is high
- Small percentage of patients do well with clinical resolution and no long term sequelae
Interstitial lung disease
- Complicating Connective Tissue Disease
- Rheumatoid Arthritis
- Systemic Lupus Erythematosis
- Progressive systemic sclerosis (Scleroderma)
- Polymyositis-dermatomyositis
- Sjogren’s Syndrome
- Overlap Syndromes
Interstitial lung disease
Connective Tissue Disorders
- Connective Tissue Disorders
- Usually patients have evidence of underlying disease first, but sometimes lung manifestations can proceed diagnosis by several years
- Pulmonary involvement is more common than clinically suspected
- Often UIP, but sometimes NSIP, or COP
- Lower lobe more common than upper lobe disease
