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
Discuss the treatment of interstitial lung disease, include:
- Conservative management
- Pharmacological management (for different causes)
- Other mangement
Conservative Management
- Remove occupational exposure
- Avoid associated drugs
- Stop smoking
- Pulmonary rehabilitiation
- Flu vaccination
Pharmacological Management (depends on cause)
- Idiopathic pulmonary fibrosis: antifibrotics (e.g. pirfenidone or nintedanib)
- Sarcoidosis: corticosteroids
- Connective tissue disease: corticosteroids & steroid sparing agents (e.g. azathioprine)
- EAA: corticosteroid
- ?High N-acetlycysteine (recent trials)
Other Management:
- Long term oxygen therapy (sats <88%)
- Treatment of infections
- MDT
- Palliation
- ?Transplantation
State some potential complications of interstitial lung disease, incldue disease related complications and treatment related complications
Disease-related complications
- Respiratory failure: due to failure of gas exchange in the lungs.
- Pulmonary hypertension: due to chronic hypoxic pulmonary vasoconstriction
- Anxiety and depression: due to impaired quality-of-life.
Treatment-related complications
- Due to long-term steroid use: osteoporosis, hypertension, Cushing’s syndrome.
- Due to antifibrotics: diarrhoea, nausea, anorexia.
Discuss the prognosis of idiopathic pulmonary fibrosis
- 50% 5 year survival rate
- Increased risk of lung cancer
For asbestosis, discuss:
- What it is
- How long following exposure symptoms/effects develop
- Potential problems causes by asbestos inhalation
- Compensation available
- Whether referral to coroner is required
- Lung fibrosis related to inhalation of asbestos. Asbestosis is both fibrogenic and oncogenic.
- Decades
- Potential problems:
- Lung fibrosis
- Pleural thickening & pleural plaques
- Adenocarcinoma
- Mesothelioma
- Suffers are eligible for compensation if develop asbestos related health conditions (except isoalted pleural plaques)
- All pts that die with known exposure to asbestos must be referred to the coroners
What is sarcoidosis?
Discuss its prevelance
- Multisystem inflammatory disorder of unknown cause that causes non-caseating granulomas to form; commonly involves respiratory system but can involve any system
- Two spikes in incidence: young adulthood & again around aged 60. Women > men. Black people more than other ethnic groups.
Discuss the symptoms/clinical signs of sarcoidosis
In 20-40% disease is discovered incidentally and pt is asymptomatic. But pt may have:
Lungs (>90%)
- Progressive dyspnoea
- Dry cough
- Chest pain
Liver (20%)
- Hepatomegaly
- Liver nodules
- Cirrhosis
Eyes (20%)
- Uveitis
- Conjuncitvitis
- Optic neuritis
Systemic symptoms
- Fever
- Fatigue
- Weight loss
- Lyphadenopathy
Skin (15%)
- Erythema nodusom
- Lupus pernio
Heart (5%)
- Bundle branch block
- Heart block
Kidneys (5%)
- Kidney stones (hypercalcaemia)
- Nephrocalcinosis
- Interstitial nephritis
CNS (5%)
- Diabetes insipidus
- Encephalopathy
- Bells palsy
… and many many more! Don’t need to learn lots just realise it can affect all organs.
What investigations would you do for sarcoidosis, include:
- Bedside
- Bloods
- Imaging
Bedside
- Pulmonary function tests: shows obstructive pattern until fibrosis occurs
- Urinary calcium: can cause hypercalciuria
- Urine dipstick or sample: proteinuria, albumin-creatine ratio
- ECG: can cause caardiomyopathy & arrhythmias
- Opthalmology: eye involvement
Bloods
- FBC:
- LFTs:liver func
- U&Es: renal func
- ESR: raised
- ACE: elevated in 60% pts
- Calcium: increased
- Serum soluble interleukin-2 receptor: raised
- Immunoglobulins: raised
Imaging
- CXR: hilar lymphadenopathy
- High resolution CT thorax: hilar lymphadenopathy & pulmonary nodules
- ECHO: look for cardiomyopathy
- MRI head: look for neuorosarcoidosis
- Abdominal ultrasound: liver & kidney involvement
- PET scan: areas of active inflammation
Others
- Tissue biopsy: granulomas
- Bronchoavleolar lavage: lymphocytes in active disease
- Bone x-rays:punched out lesions
What might you see on CXR of someone with sarcoidosis
- Bilateral hilar lymphadenopathy
- Evidence of pulmonary fibrosis
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
State some common causes of bilateral hilar lymphadenopathy you need to be aware of
- Sarcoidosis
- TB
- Malignancy
- Amyloidosis
- Hypersensitivity pneumonitis
What is the gold standard for diagnosing sarcoidosis?
Histology from biopsy
Usually done by doing bronchoscopy with ultrasound guided biopsy of mediastinal lymph nodes
Acute sarcoidosis may present with Lofgren syndrome; what is Lofgren syndrome?
Discuss the treatment of sarcoidosis
- No treatment in pts with no or mild symptoms as condition resolves spontaneously
- Oral steroids are first line, for 6-12 months, if treatment is required. NOTE: pts should be given biphosphonates to protect agains osteoperosis
- Second line: azathioprine, methotrexate
- Lung transplant = rare
Discuss the prognosis of sarcoidosis
- Spontaneously resolves in 6 months in 60% pts
- In small number progresses to pulmonary fibrosis and pulmonary hypertension- potentially require lung transplant
- Death is usually when it affects heart causing arrhythmias or CNS
State some examples of specific causes of hypersensitivity pneumonitis (AKA extrinsinc allergic alveolitis) (4)
- Bird-fanciers lung: reaction to bird droppings
- Farmers lung: reaction to moudly spores in hay
- Mushroom worker’s lung: reaction to specific mushroom antigens
- Malt workers lung: reaction to mould on barley
