Interstitial Lung Disease Flashcards
What is meant by interstitial lung disease?
Umberella term used to describe number of conditions that affect lung parenchyma in a diffuse manner; they cause inflammation and fibrosis of the alveoli, the distal airways, and interstitium from a variety of insults (hence interstitial lung disease is a misnomer). They are characterised by chronic inflammation and/or progressive fibrosis.
Interstitial lung disease is also referred to as…?
Diffuse parenchymal lung disease (DPLD)
Briefly discuss the pathophysiology of interstitial lung disease
- Some ILDs (e.g.sarcoidosis) are predominantly inflammatory, with little fibrosis. This inflammation is mediated by innate and adaptive immune cells and may resolve.
- Other ILDs (such as idiopathic pulmonary fibrosis) are characterised by fibrosis in the lung interstitium, which is irreversible. Fibrosis is triggered by repeated injury to the lung tissue (e.g. from inhaled toxins). Usually, fibroblasts respond to this lung injury by secreting extracellular matrix, which repairs the injuries. In ILD, genetic mutations lead to excess secretion of extracellular matrix, which accumulates in the lung interstitium, leading to fibrosis.
- The lung interstitium becomes thicker, increasing the diffusion distance for oxygen to travel from the air in the alveoli to the blood in the surrounding capillaries. Hence, gas exchange in the lungs is compromised.
There are many different types (>200) of interstitial lung disease; classification is complex and constantly changing. For your purposes you can split interstitial lung disease into two broad categories and then further subcategories.
State the two broad cateogories and their subcategories
Primary ILD (unknown cause):
We can then further classify this based on histological & radiological appearance. Some examples include:
- Usual interstitial pneumonia (UIP)/ Idiopathic interstitial pneumonia see below for explanation
- Non-specific interstitial pneumonia (NSIP)
- Desquamative interstitial pneumonia (DIP)
- ….etc
Secondary (known cause):
We can then further classify these based on the cause:
-
Connective tissue & autoimmune disease
- Sarcoidosis
- RA
- SLE
- Sjogren’s
-
Infective
- Mycoplasma pneumonia
- Pneumocystis pneumonia
- TB
-
Environmental/occupational
- Asbestos
- Silicosis
- Berylliosis
- Extrinsic allergic alveolitis
-
Drugs
- Methotrexate
- Amiodarone
- Bleomycin
- Nitrofurantoin
- Cyclophosphamide
For ILD that are primary, we use histological and radiographic appearance to help classify. Usual interstitial pneumonia is the commonest hisological/radiological appearace. Of the ILD that have UIP appearance, idiopathic pulmonary fibrosis is the most common. So sometimes will hear them used interchangeably- but they are not exaclty interchangeable
State some risk factors for developing interstitial lung disease
- Male
- Smoking
- Regular dust exposure
- Associated systemic disorder
Why is it important to take a comprehensive occupational/environmental history in someone with suspected ILD?
Might help you determine cause of ILD. Occupational/enviromental causes include:
Inhalation of industrial dust
- Coal workers pneumoconiosis
- Silicosis (exposure to silica particles e.g. metal mining, stone quarrying, pottery/ceramics)
- Asbestosis (inhalation of asbestos e.g. in building trade)
- Beryilliosis
Inhalation of organic antigens (causes Extrinsic Allergic Alveolisits)
- Farmers (hay dust & aspergillus mould)
- Bakers (flour dust & additive enzymes)
- Mould/pets: protein in bird droppings cause cause
State the symptoms of interstitial lung disease
- Progressive exertional dyspnnoea
- Dry cough
- General malaise & fatigue
- Symptoms of underlying disease (if this is cause) e.g:
- SLE: discoid rash
- RA: pain in joints
- Sjogrens: dry mouth and eyes
- Sarcoidosis:
State what you might find on clinical examination of someone with interstitial lung disease
- Clubbing
- Reduced chest expansion
- Cyanosis
- Wheeze
- Fine inspiratory crackles (like velcro, usually heard best at basal/axillary area)
-
Features of pulmonary hypertension:
- Raised JVP
- Hepatomegaly
-
Systemic findings if due to underlying disease:
- Skin Changes
- Eye Changes
- Salivary Gland enlargement
- Peripheral Lymphadenopathy
What investigations might you do for someone with suspected interstitial lung disease, include:
- Bedside
- Bloods
- Imaging
Bedside
- Urine dipstick: haematuria may indicate vasculitis
- Spirometry: restrictive pattern
Bloods
- FBC: may showaneamia of chronic disease
- CRP: inflammation
- ESR: inflammation
- Autoimmune antibodies: see next card
Imaging
- CXR
- High resolution CT
What investigations would you are newly diagnosing someone with intertsitial lung disease?
Most of investigations revolve around either identifying an underlying cause or excluding all underlying causes. Tests that you do to include/exclude causes are:
- ANA: autoimmune cause
- ENA: allows you to determine more specific autoimmune cause as can look at e.g. Anti-SM, Anti-Ro etc..
- RhF: if rheumatoid suspected
- ANCA: vasculitis
- Anti-GBM: Goodpasture’s
- ACE: high ACE can indicate sarcoidosis
- IgG to serum precipitins: useful for detecting extrinsic allergic alveolitis (EAA) by detecting antibodies to allergens
- HIV: immuncompromised. Increased likelihood of ILD
Describe what you might see on CXR of someone with interstitial lung disease?
- Reticular fine opacities.
- Location can help indicate cause (see image)
Describe what you might see on CT scan of someone with interstitial lung disease
Some ILDs, especially idiopathic pulmonary fibrosis, show a “usual interstitial pneumonia” pattern, which includes:
- Honeycombing (clusters of cystic airspaces)
- Traction bronchiectasis (dilated airways, which are pulled apart by areas of surrounding fibrosis)
- Reticular opacities (thickening of the lung interstitium)
What invasive investigations may you need to do to help determine cause of interstitial lung disease?
- Bronchoalveolar lavage: bronchoscope is inserted into the airways, and sterile saline is injected through the bronchoscope into the airways. The saline is then collected via suction and analysed. This helps to diagnose the underlying cause of the ILD, and to also exclude infection or malignancy.
- Trans-bronchial biopsy/surgical lung biopsy: a small sample of lung is collected and then analysed by a pathologist. This may be needed if previous tests are inconclusive, or if a tissue sample is needed to make the diagnosis.
Extrinsic Allergic Alveolitis/EAA (also known as hypersensitivity pneumonitis) a category in classification of interstitial lung disease.
- Describe what EAA is
- Compare acute and chronic presentation of EAA- include time scales, symptoms, reversibility
- How do we diagnose
- Management
- Type III hypersensitivity reaction to environmental allergen that causes parenchymal inflammation & destruction in people that are sensitive to that allergen.
Presentations
-
Acute:
- Presents 4-8hrs following exposure
- Fever, rigors, dry cough, dyspnoea
- Usually reversible
- Spontaenously settle in 1-3 days
-
Chronic
- Presents months-years later after chronic exposure
- Finger clubbing, increasing dyspnoea, decreased weight, cor pulmonale
- Less reversible
- Diagnose by bronchoalveolar lavage (involves collecting cells from airways during bronchoscopy by washing airways with fluid then collecting fluid for testing). Shows raised lymphocytes & mast cells.
- Management: remove allergen, steroids & oxgyen where necessary
What is cryptogenic organising pneumonia?
- Bronchiolitis obliterans organising pneumonia
- Focal area of inflammation of lung tissue; can be idiopathic or triggerd by infection, inflammatory disorders, medications, radiation or environmental toxins or allergens
- Very similar presentation to pneumonia & has similar CXR features (e.g. focal consolidation)
- Diagnosis requires lung biopsy (often delayed as it presents so similar to infective pneumonia)
- Treatment: systemic corticosteroids
Describe the 4 stages of sarcoidosis on CXR
- 1= bilateral hilar lymphadenopathy
- 2= BHL + peripheral pulmonary infiltrates
- 3= peripheral pulmonary infiltrates alone
- 4= progressive pulmonary fibrosis, bulla formation, pleural involvement
Acute sarcoidosis may present with Lofgren syndrome; what is Lofgren syndrome?
