interstitial lung disease Flashcards
what is interstitial shadowing
Reticular eg linear, lace like patter
Too many lug markings
May be focal or diffuse
what is the interstitium
Refers to supporting structures of the lung
Includes: alveolar endothelium, capillary endothelium, basement membrane, connective tissue
In disease it can be thickened by
Fluid, cells, fibrosis
what is the extracellular matrix
3D fibre mesh filled with macromolecules eg. Collagen, elastin
Several functions
Tensile strength/elasticity
Low resistance for effective gas exchange
Tissue repair/remodelling
In fibrosis, aberrant wound healing leads to excessive deposition in the interstitium
how are ILDs classified
Environmental exposures Occupational lung disease Silicosis (silica exposure) Coal miners lung (coal dust exposure) Asbestosis (asbestos exposure) Hypersensitivity pneumonitis (mould and bird proteins are common causes) Idiopathic Idiopathic pulmonary fibrosis is the prototypical ILD Systemic inflammatory diseases Connective tissue disease-ILD Sarcoidosis
how can classification be simplified
connective tissue disease, hypersensitivity pneumonitis, sarcoidosis, drug, occupational
no cause- idiopathic
how does idiopathic pulmonary fibrosis present
Symptoms and clinical signs of IPF appear gradually and include
Slowly progressive exertional dyspnoea
Non-productive cough
Dry, inspiratory bibasal ‘velcro’ crackles
Possibly clubbing
Abnormal pulmonary function test results (restriction and impaired gas exchange)
what is the IPF HRCT pattern
basal distribution, sub pleural, honeycombing, traction bronchiectasis
if present - no biopsy needed
how can IPF be summarised
Progressive, irreversible fibrosis and is fatal
Limited to lungs – unlike other ILDs like sarcoidosis
Affects lower and peripheral lungs
Minimal inflammation – no role for steroids
Disease of older age (median age of 66)
2x as common in men
More common in smokers (60%)
HRCT = most diagnosis but lung biopsy may be needed
how does IPF impact the UK
Approx 6000 new cases each year
Increasing by 5% each year
>32000 living with it
1/100 deaths
what is the prognosis of IPF
Median survival is 3 years from diagnosis
But 20% still alive after 5
No reliable way to predict
Live with considerable uncertainty
How is IPF managed
Assess suitability for anti fibrotic drugs
Pirfenidone or nintedanib
Can only be prescribed by specialist centres
Aim to slow rate of progression
what is the criteria for IPF treatment
Diagnosis of IPF
FVC 50-80% predicted
drugs often poorly tolerated – weight loss, GI upset and photosensitivity
Assess suitability for lung transplant (<65, no sig comorbidities)
Offer best supportive care to all
how can the best supportive care for IPF be provided
stepwise decline- intervene and treat (acute infection, PE, pneumothorax, acute exacerbation) treat comorbidities (GORD, COPD, lung cancer) Palliate symptoms (LTOT, Pulmonary rehab, benzos, opiates) refer to palliative care
what is hypersensitivity pneumonitis
Diffuse inflammation of parenchyma is response to inhaled antigen – teds to involve upper lobes Bird-fanciers (bird droppings) Farmers lung (thermophilic) Aspergillus (ubiquitous fungus) Antigen unknown in 50%
how does HP present
Acute
SOB, cough, fever and crackles within 4-6 hours of heavy exposure
Often misdiagnosed as infection
Most develop after years of continuous or intermittent inhalation of inducing aget
Sub-acute
Gradual onset of symptoms, wight loss common
Chronic
Insidious onset, history of acute episodes may be absent
Incomplete resolution with removal of antigen
May lead to irreversible fibrosis
how is HP diagnosed
Serum precipitins (circulating igG antibody-antigen complexes) to specific antigen may be helpful
Infinite number of possible antigens
May be positive in asymptomatic individuals
Negative result does not exclude HP
how is HP managed
Avoid inciting antigen
Usually steroid-responsive in early disease
May progress to irreversible fibrosis
how is drug-induced ILD diagnosed
Medication history important – specific questions
Many common drugs are nitrofurantoin, amiodarone, methotrexate
Always consider if medication may be implicated
Association between initiation of drug and onset of disease important but ILD may develop months-years after starting the drug
what is connective tissue disease-related ILD
Rheumatoid arthritis, sjogrens, scieroderma, polymyositis
Younger patients, female predominance
Detailed history – dry eyes/mouth, raynaud’s, joint pain/swelling, rashes
Bloods – antinuclear antibodies, rheumatoid factor
Management – liaise with rheumatology, treat underlying disease (biologics, steroids, immunosuppression)
How are ILDs diagnosed
Clinical assessment – identifiable cause
CTD symptoms, drugs, exposures
Bloods – ANA, RF, angiotensin-converting enzyme (ACE)
Spirometry/lung function tests
FVC, FEV1/FVC ratio (normal or high), gas transfer (may have co-existent COPD)
CXR – reticular shadowing
HRCT pattern of disease – cornerstone of diagnosis but only 60% are diagnostic
Lung biopsy – enhances diagnosis but risk often outweighs the benefit, may differentiate IPF from other potentially reversible causes
how are ILDs treated
MD1 for diagnosis
Respiratory physician, respiratory radiologist, rheumatologist (+ specialist histopathologist)
Combo of history, HRCT pattern of disease, auto-immune bloods
Remove cause.
Immunosuppression (prednisolone, hydroxychloroquine, mycophenolate mofetil, methotrexate)
Anti-fibrotics for IPF
what is sarcoidosis
Multisystem granulomatous disorder – non-necrotising granulomas
Cause unknown – 3x more common in afro-caribbeans, more severe disease, some familial clusters
Disease of the young – 75% 30-60 years
Unpredictable clinical course
what is the histology of sarcodosis
Characterised by granulomatous inflammation
Unknown foreign antigen stimulates immune response including
CD4+ cells, alveolar macrophages, multi-nucleate giant cells
Organise into granulomas
Granulomas occur in TB and fungal infections but in sarcoidosis they are non-necrotising
A biopsy demonstrating granulomas along with clinical picture is needed to confidently diagnose
how does sarcoidosis manifest
Can effect any organ – lung involvement 90%
Lung and thoracic lymph nodes – dyspnoea, cough, chest pain, pulmonary hypertension, mixed pulmonary function test, abnormalities (obstruction, restriction, diffusion, deficits)
how does sarcoidosis commonly present
chest - cough, SOB, wheeze, incidental finding
skin - erythema nodosum, lupus permit, plaques, nodules
eyes- anterior uveitis
lymph node biopsy- suspect malignancy
hypercalcaemia
peripheral nerves- Bell’s palsy, mono neuropathies
what is lofgren’s syndrome
Erythema nodosum
Bilateral hilar lymphadenopathy
Arthalgia
Excellent prognosis, usually self limiting
what are the symptoms of pulmonary sarcoidosis
May be asymptomatic (especially with isolated lymphadenopathy)
Cough, dyspnoea, chest tightness
Systemic symptoms: fatigue, sweats, weight loss, fevers, arthalgia
how does pulmonary sarcoidosis progress
2/3 remission and 1/3 chronic disease(inflammation can = fibrosis)
variable clinical course
stages
lymphadenopathy, LA + infiltrates, infiltrates and fibrosis
may be asymptomatic despite significant CXR abnormalities
how is sarcoidosis diagnosed
No single diagnostic test
Combo of clinical picture, exclusion of alternative diagnosis (esp lymphoma and TB)
Baseline tests – renal, liver function, calcium, serum ACE, CXR, ECG
Serum ACE
Secreted by activated alveolar macrophages in granulomas, low sensitivity (60%), poor specificity
Polymorphisms in ACE gene – variation in peripheral blood ACE levels
No correlation with CXR stage of disease
Biopsy everything – skin, lymph nodes, blind endobronchial biopsies (44-70% yield)
what are the types of sarcoidosis
Major organ involvement – ocular disease not responding to topical treatment, cardiac, neurological
Less clear-cut pulmonary disease – often less severe than extra-thoracic disease with spontaneous remission common, short term symptomatic benefit, long term effect on natural history of disease not known
how is sarcoidosis treated
Corticosteroids for 6-24 months are mainstay – inhaled corticosteroids may give symptomatic benefit, additional immunosuppressants eg methotrexate, azathioprine may be necessary
what might spirometry reveal on lung function tests
obstructive - problem in airways, useful Dx (reversible - asthma, fixed and smoker - COPD)
only a few other airway disease (bronchiectasis, obliterative bronchiolitis)
restrictive - problem but not useful Dx, useful for monitoring change (acute, chronic or risk of ventilatory failure), treatment criteria for IPF
what is restrictive spirometry
Restriction of lung expansion or loss of lung volume
Directly measured by TLC – requires lung function lab
FVC reflects the TLC – can be done in clinic and useful for disease monitoring
Think anatomically to explain
what can cause restrictive spirometry
Skin – extensive burns, scleroderma
Subcutaneous tissues – raised BMI
Thoracic cage – Kyphoscoliosis
Neuromuscular system – eg MND, guilian-barre
Pleura – thickening
Loss of lung vol – pneumonectomy, pleural effusion
Lung parenchyma – ILD
what do lung function tests show for ILD
Fibrotic lungs small and stiff
Higher elastic recoil than expected for volume
FEV1/FVC ratio may be high – but also may be normal
TLCO (gas transfer) – impaired gas exchange due to disruption of alveolar-capillary interface or reduced total surface area
FVC and TLC dec
compliance dec intrinsic or normal extrinsic
