Interstitial Lung Diseases Flashcards
The interstitium
Alveolar endothelium Capillary endothelium Basement membrane Connective tissue In disease, it can be thickened by fluid, cells, fibrosis
Extracellular matrix
3D fibre mesh filled with macromolecules e.g. collagen/elastin
Functions: tensile strenght/elasticity, low resistance for effective gas exchange, tissue repair/modelling
In fibrosis, aberrant wound healing leads to excessive deposition in the interstitium
Classification
Environmental exposure: Occupational lung disease (silicosis, coal miners lungs, abestosis); hypersenstivity pneumonitis (mould and bird proteins are common causes)
Idiopathic: Idiopathic pulmonary fibrosis is the protypical ILD
Systemic Inflammatory Disease: connective tissue disease - ILD, sarcoidosis
Idiopathic Pulmonary Fibrosis - presentation
Symptoms and clinical signs often appear gradually and include:
slowly progressive exertional dyspnoea; non productive cough; dry, inspiratory bibasal crackles; +/- clubbing of fingers; abnormal pulmonary function test results
IPF summary
Unknown cause; causes progressive, irreversible fibrosis and is fatal; is limited to the lungs; affects lower peripheral lung; minimal inflammation; is a disease of older age; is more common in men; is more common in smokers; HRCT is mainstay of dx but lung biopsy may be needed
Management of IPF
Assess suitability for anti-fibrotic drugs (Pirfenidone or Nintedanib); can only be one prescribed by specialist centres; aim is to slow rate of disease progression
Criteria: diagnosis of IPF, FVC 50-80% predicted, often poorly tolerated
Assess suitability for lung transplant: age <65, no significant comorbidities
Hypersensitivity Pneumonitis
Diffuse inflammation of parenchyma in response to inhaled antigen - tends to involve upper lobes (bird fanciers, farmers lung, aspergillus, can be anything, antigen unknown in 50%)
Acute - SOB, cough, fever, malaise, crackles, often misdiagnosed
Subacute - gradual onset of symptoms, weight loss common
Chronic - insidous onset, incomplete resolution with removal of antigen, may lead to irreversible fibrosis
Serum Precipitins (circulating IgG antibody-antigen complexes - infinite number of possible antigens, may be positive in asymptomatic individuals, negative result doesn’t exclude HP
Drug induced - medication important to ask in history (nitrofurantoin, amiodarone, methotrexate)
Management of HP
Avoidance of inciting antigen
Usually steroid-responsive in early disease
May progress to irreversible fibrosis
Connective Tissue Disease-related ILD
Rheumatoid arthritis, siogrens, scieroderma, polymyositis
Younger patients
Female preponderance
Detained Hx: dry eyes/mouth, Raynaud’s, joint pain/swelling, rashes
Bloods: antinuclear antibodies, rheumatoid factor
Management: liaise with rheumatology, treat underlying disease (biologics, steroids, immunosuppression)
ILD Diagnosis
Clinical Assessment (CTD symptoms, drugs, exposures)
Bloods (antinuclear abs, rheumatoid factor, angiotensin-converting enzyme (ACE)
Spirometry (FEV, FEV/FVC ratio, gas transfer)
CXR (reticular shadowing)
HCRT pattern of disease (but only 60% are diagnostic)
Lung biopsy (enhances diagnosis, but risk often outweigh benefit, may differentiate IPF from other potentially reversible causes)
ILD treatment
MDT for diagnosis: resp physical, resp radiologist, rheumatologist, +/- specialist, histopathologist; combination of history, HRCT pattern of disease, autoimmune bloods
Treatment: remove cause, immunosuppression, anti-fibrotics for IPF
Sarcoid
Mutli-system granulomatous disorder - non-necrotising granulomas
Cause unknown (3x more common in Afro-Caribbeans & more severe disease)
Disease of the young (75% if cases 30-60 yrs)
Unpredictable clinical course
Histology of Sarcoid
Characterised by granulamatous inflammation
Unknown foreign antigen stimulates immune response including CD4+ T 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 sarcoidosis
Common Presentations of Sarcoidosis)
Chest: cough, SOB, wheeze, incidental finding on CXR (all especially common in pulmonary sarcoidosis - and some systemic symptoms)
Skin: erythema nodosum, lupus pernio, plaques, nodules
Eyes: anteror uveitis
Lymph node biopsy: performed for suspected malignancy
Hypercalcaemia
Peripheral nerves: Bell’s palsy, mononeuropathies
Systemic: fever, sweats, weight loss, fevers, arthralgia
Lofgren’s Syndrome
Erythema nodosum Bilareral Hilar Lymphadenopathy Arthralgia Excellent prognosis Usually self limiting
