Fibrotic lung disease (RESP) Flashcards
Define interstitial lung disease.
Group of disorders characterised by inflammation and progressive scarring (fibrosis) of the lungs
What are some causes of interstitial lung disease? (5)
- idiopathic pulmonary fibrosis (IPF)
- hypersensitivity pneumonitis (extrinsic allergic alveolitis) - people with chronic exposure to bird droppings
- pneumoconiosis (asbestosis) - people in coal mining industry
- substance-induced (amiodarone, nitrofurantoin, methotrexate, bleomycin - chemo drug)
- secondary to underlying disease e.g. connective tissue disorders, sarcoidosis, vasculitis
Who can hypersensitivity pneumonitis (interstitial lung disease) occur in?
People with chronic exposure to bird droppings
What is the pathophysiology of hypersensitivity pneumonitis (interstitial lung disease)?
Type 3 hypersensitivity-induced lung damage due to variety of inhaled organic particles
Who does pneumoconiosis AKA asbestosis (interstitial lung disease) happen in?
People in the coal mining industry
How does pneumoconiosis (interstitial lung disease) present?
Asymptomatic but may lead to progressive massive upper zone fibrosis which is symptomatic
What underlying diseases can cause interstitial lung disease? (3)
- connective tissue disorders
- sarcoidosis
- vasculitis
What is the most common type of interstitial lung disease?
Idiopathic pulmonary fibrosis - diagnosed when there is no other identifiable cause, rare form of fibrotic lung disease with no known aetiology
Who does idiopathic pulmonary fibrosis tend to affect?
Men 50-70 years old
What is idiopathic pulmonary fibrosis characterised by?
Scar tissue formation within lungs, dyspnoea, significantly shortened lifespan after diagnosis
List the causes of upper zone fibrosis. (6)
CHARTS
- Coal workers pneumoconiosis
- Histiocytosis/Hypersensitivity pneumonitis
- Ankylosing spondylitis
- Radiation
- Tuberculosis
- Sarcoidosis/silicosis
List the causes of lower zone fibrosis. (4)
DIAL
- Drugs - amiodarone, nitrofurantoin, methotrexate, chemo (bleomycin)
- Idiopathic pulmonary fibrosis
- Asbestosis
- Lupus (and other CTDs except ankylosing spondylitis)
Describe the aetiology of interstitial lung disease.
- occurs in genetically predisposed individuals
- recurrent injury to alveolar epithelial cells –> secretion of cytokines and growth factors by pneumocytes especially TGFb1
- usually there is interstitial tissue in between alveoli and capillaries containing fibroblasts and macrophages
- cytokines cause fibroblast activation, recruitment, proliferation, differentiation into myofibroblasts and increased collagen synthesis and deposition –> thickened interstitial layer –> problems with ventilation and oxygenation + stiffer alveoli
Is interstitial lung disease obstructive or restrictive?
Restrictive - restricted lung expansion due to fibrosis of interstitium
What is interstitial lung disease characterised by?
Honeycombing: loss of alveoli –> fluid-filled cysts surrounded by thick wall
What are the clinical features of interstitial lung disease? (6)
- gradual onset
- progressive dyspnoea - initially on exertion, then progresses to dyspnoea at rest
- chronic dry cough
- bibasal fine end-inspiratory crackles on auscultation
- weight loss, fatigue, malaise
- digital clubbing
What might you see on examination of interstitial lung disease? (4)
- bibasal fine end-inspiratory crackles
- clubbing (chronic disease)
- cyanosis
- signs of right heart failure (advanced disease)
What are the risk factors for interstitial lung disease? (9)
- advanced age
- male sex
- family Hx
- gene mutations and nucleotide polymorphisms
- cigarette smoking
- occupational and environmental exposures
- GORD
- viral/bacterial infection
- diabetes
What are the first-line investigations for interstitial lung disease? (3)
- CXR
- high-resolution CT (HRCT) chest
- pulmonary function tests (spirometry)
What do we see on spirometry in interstitial lung disease?
- restrictive lung disease pattern (reduced FEV1, significantly reduced FVC, increased FEV1/FVC ratio >0.7)
- reduced TLCO (total capacity of the lung for CO)
- decreased lung volume and compliance
What do we see on HRCT in interstitial lung disease?
- honeycombing
- multiple cystic lesions within lung parenchyma due to fibrosis, ‘ground glass’ appearance
What do we see on CXR in interstitial lung disease? (5)
- bilateral lower zone reticulonodular shadowing
- honeycombing
- ground-glass appearance
- signs of cor pulmonale
- shaggy heart borders
What is the gold standard investigation for idiopathic pulmonary fibrosis?
High resolution CT
What might you see on bloods in interstitial lung disease?
- raised CRP
- raised Ig
- ABG - normal in early disease, pO2 decreases with exercise, pCO2 rises in late stage disease
- ANA and RF (1/3 will be positive)
- anti-CCP and myositis panel to rule out collagen vascular disease
