Interstitial lung disease Flashcards
What are the known causes under the category of Diffuse Parenchymal Lung Disease of known cause?
Drug
1) Cytotoxics (chemotherapeutics): MTX, AZA, bleomycin, bulsulphan, cyclo, chlorambucil
2) CNS: amitryptiline, phenytoin, carbamazepine
3) CVS: amiodarone, hydralazine, procainamide
4) ABX: nitrofurantoin, isoniazid
5) Antirheumatics (DMARTS): gold, sulphasalazine
6) Radiation, aspirin, oxygen
* *= important
Connective tissue disease
- RA: There is bilateral involvement of the small joints of the hands, causing ulnar deviation of the MCPJ, swan neck deformity of the fingers, and Z thumb – indicating a RA picture
- SLE
- Dermatomyositis
- Sjogren’s
- Systemic sclerosis
Miscellaneous: don’t need to know - Langerhan cell histocytosis Lymphangioleiomyomatosis (LAM) - Alveolar proteinosis - Post-infectious
What are the known causes under the category of Granulomatous Diffuse Parenchymal Lung Disease?
Sarcoidosis
Hypersensitivity pneumonitis 🡪 due to violent IR against any insult to the lungs. Important if patient keeps exotic pets at home / go overseas to amazon jungle etc
How is idiopathic interstitial pneumonia (IIPs) categorized?
Chronic fibrosing
- idiopathic pulmonary fibrosis: most common & most important to know
- idiopathic nonspecific interstitial pneumonia
Acute/ subacute fibrosing
- Cryptogenic organising pneumonia: responds well to steroids, Cryptogenic = obscure / uncertain origin
- Acute interstitial pneumonia 🡪 rapid onset, diagnosis usually post-mortem
Smoking related 🡪 because smoking cessation can lead to improvement
- Respiratory bronchiolitis interstitial lung disease
- desquamative interstitial pneumonia
What are the causes of interstitial lung disease that manifests in the upper lobe?
Rule: tend to be caused by INHALED substances as upper lobe V>Q
Coal worker pneumoconiosis
- Pneumoconiosis = inflamm of lungs due to inhalation of dust 🡪 causing cough , inflamm and fibrosis
Histiocytosis – a group of immune conditions that causes an increase in histiocytes (aka tissue macrophages such as Langerhans cells) – wrt ILD, refers to increased histiocytes in the lung (Pulmonary Langerhans cell histiocytosis)
Ankylosing spondylitis, ABPA (will have eosinophilic picture)
- ABPA: allergic Bronchopulmonary Aspergillosis
- AS: the exception to the rule
Radiation – possibly from Breast CA radiation
TB
Silicosis, sarcoidosis
- Silicosis = a type of occupational lung disease caused by inhalation of silica dust
What are the causes of interstitial lung disease that manifests in the lower lobe?
Lower Lobe (RASIO) RA - Asbestosis - Scleroderma - Idiopathic pulmonary fibrosis - Others (drugs)
What are the causes of interstitial lung disease that manifests in the upper+ lower lobe?
Upper + Lower - “NEPAL”
- Neurofibromatosis, tuberculous sclerosis
- Extrinsic allergic alveolitis
- Pulmonary haemorrhagic syndromes
- Alveolar proteinosis
- Lymphangiomyomatosis
What are the more likely etiologies of ILD in patients 20- 40 years old?
Sarcoidosis, connective tissue disease, Lymphangioleiomyomatosis, Langerhans cell histiocytosis, other inherited forms
What are the more likely etiologies of ILD in patients >50 years old?
Idiopathic pulmonary fibrosis
What are the symptoms experienced by someone with interstitial lung disease?
Generally nonspecific Symptoms
- Cough (usually dry 🡪 differentiates from bronchiectasis)
- Exertional dyspnoea
- Rare: Wheezing and haemoptysis
Systemic Review (for connective tissue diseases):
- Instead of findings specific for ILD, we may get findings indicating underlying aetiology (eg: connective tissue disorder)
1) Any Hx of Rheum / AI dz; joint pain, rash, eye redness
2) Drug Hx and Social Hx – workplace exposure
3) Hx of TB exposure – night sweats, LOW, LOA
What are the signs seen in someone with ILD?
Disease Findings
- Tachypnoea
- Clubbing
- Reduced chest expansion
- Bilateral, Fine, Velcro-like, end inspiratory crepitation (usually heard at bases)
S&S of Complications
- Signs of cor pulmonale/pulmonary hypertension/polycythaemia (from prolonged hypoxia): Elevated JVP, Pedal edema, Palpable P2, Parasternal heave
- Signs of respiratory distress: Tachypnoea, using accessory respi muscles, supplemental O2
S&S of Aetiology
- RA: deforming symmetrical polyarthropathy, rheumatoid nodules
- SLE: malar rash
- Scleroderma: CREST Syndrome (Calcinosis, Reynaud’s, Esophageal Dysmotility, Sclerodactyly, Telangiectasia)
- Dermatomyositis: Gottron’s papules, mechanics hands, shawl/V sign, heliotrope rash, proximal myopathy
- Sarcoidosis: Uveitis, salivary gland enlargement, lymphadenopathy, hepatosplenomegaly
What are the investigations required for diagnosis of ILD?
CXR
- Bilateral heterogenous diffuse reticulo-nodular opacities / Reticular Shadowing (hallmark)
- Reticular = Net-like; multiple fine lines crossing each other
- Caused by thickening of interstitium from inflammation or fibrosis
HRCT (may provide etiology in certain cases)
- HRCT makes thinner cuts which are wider apart
- Subpleural/ Basal-predominant reticular abnormalities (sensitive for IPF)
- Honeycombing / reticular changes 🡪
- May have bronchiectatic changes – traction bronchiectasis (pulling of the airways open from fibrosis)
Lung Function Tests
- Spirometry: restrictive picture (↑ or normal FEV1/FVC)
- Lung volume (↓ TLC ↓ VC)
- Diffusion test (reduced DLCO): Extent that O2 is able to pass from alveoli into blood
- 6-minute walk test : Look for any desaturation during and after test. Baseline measurement for monitoring
What are the investigations required for etiology of ILD?
Bloods
1) IGRA / T Spot test / Tuberculin skin test
2) Autoimmune workup:
- ANA (SLE), anti-dsDNA (more specific for SLE), C4=3, C4, anti-Ro/La (in SLE and Sjogerns), anti-RF (RA), anti-CCP (RA) first.
- If negative, check the rest Scleroderma (anti-Scl-70) & Dermatomyositis (anti-Jo1, antisynthetase, CK).
3) ESR/CRP
4) Calcium : If raised 🡪 sarcoidosis?
5) Retroviral Screen: HIV 🡪 mimicker of diseases
Bronchoalveolar Lavage
1) Lavage for sputum 🡪 to send for culture and other tests
2) Evaluation of patients with:
- Haemoptysis,
- Acute or rapidly progressive ILD
- Likely caused by one of the following diseases: sarcoidosis, hypersensitivity pneumonitis, pulmonary Langerhans histiocytosis, or infection
Lung Biopsy
- Transbronchial (only can access central lung) or surgical
- Only if uncertain of diagnosis – esp for non-cryptogenic causes of ILD, there may not be characteristic features of honeycombing and traction bronchiectasis
Others
- Sarcoidosis: check serum ACE, prominent hilar lymphadenopathy on HRCT
- Hypersensitivity pneumonitis: screen for antibody to the suspected antigen
- Vasculitis: ANCA, urinalysis
What are the investigations required for complications of ILD?
ECG/Echocardiogram – to look for heart function
- Pulmonary hypertension
- Right HF
What is the definition of idiopathic pulmonary fibrosis?
- Specific form of chronic, progressing, fibrosing interstitial pneumonia of unknown cause
- Associated with characteristic histopathologic and or radiologic pattern (see below)
- Dx of exclusion – Rule out smoking-related, cryptogenic organising pneumonias (due to adjacent infection)
What is idiopathic pulmonary fibrosis associated with?
Smoking – particularly >20 pys
GERD (90%) – can potentially worsen IPF (microaspiration of acidic contents)
- When taking respi history 🡪 should always cover GERD. GERD causes aspiration which worsens a lot of respi syndromes hence is always important to ask!
CAD, OSA, COPD
Environmental (metal/wood dust, farming, birds, etc.)
