interstitial lung diseases Flashcards
what is the interstitium?
supporting structures of the lungs: alveolar endothelium, capillary endothelium, basement membrane, connective tissue
what thickens the interstitium?
fluid, cells and fibrosis
what are the functions of the extracellular matrix?
- tensile strength/elasticity
- low resistance for effective gas exchange
- tissue repair/modelling
what happens to the extracellular matrix during fibrosis?
aberrant wound healing leads to excessive deposition in the interstitium
what are the simple classifications of interstitial lung diseases?
- idiopathic
- sarcoidosis
- connective tissue disease
- hypersensitivity pneumonitis
- drugs
what are the symptoms and clinical signs of IPF?
- slow progressive exertional dyspnoea
- non-productive cough
- dry, inspiratory bibasal velcro crackles
- +/- clubbing of fingers
- abnormal pulmonary function test results: restriction impaired gas exchange
what is the summary of IPF?
- unknown cause
- causes progressive, irreversible fibrosis and is fatal
- is limited to the lungs
- affects lower and peripheral lung
- minimal inflammation: no role for steroids
- is a disease of older (median age 66 years)
- is more common in men
- is more common in smokers
- HRCT is mainstay of dx but lung biopsy may be needed
how do you manage IPF?
assess suitability for anti-fibrotic drugs
- pirfenidone and nintedanib
- can only be prescribed by specialist centres
- aim is to slow rate of disease progression
criteria
- diagnosis of IPF
- forced vital capacity (FVC) 50-80%
assess suitability for lung transplant
- age <65
- no significant comorbidities
how do you get hypersensitivity pneumonitis?
- bird droppings
- farmers lungs
- aspergillus
- antigen is unknown 50%
what is hypersensitivity pneumonitis?
- diffuse inflammation of parenchyma in response to inhaled antigen
- tends to involve upper lobes
how does acute hypersensitivity pneumonitis present?
- dyspnoea, cough, fever, malaise, crackles within 4-6 hours of heavy exposure
- often misdiagnosed as an infection
how does subacute hypersensitivity pneumonitis present?
gradual onset of symptoms, weight loss is common
how does chronic hypersensitivity pneumonitis present?
- insidious onset, history of acute episodes may be absent
- incomplete resolution with removal of antigen
- may lead to irreversible fibrosis
how do you diagnose hypersensitivity pneumonitis?
serum precipitins to specific antigen may be helpful
- infinite number of possible antigens
- may be positive in asymptomatic individuals
- negative results do not exclude HP
how do you manage hypersensitivity pneumonitis?
- avoidance of inciting antigen
- usually steroid-responsive in early disease
- may be progress to irreversible fibrosis
what are the characteristics of drug induced ILD?
- medication history is very important
- many drugs but most common: nitrofurantoin, amiodarone, methotrexate
- always consider if medication may be implicated
- association between initiation of drug and disease onset is important
- ILD may develop months to years after starting the drug
what are the characteristics of connective tissue disease related ILD?
- rheumatoid arthritits
- scleroderma
- sjogrens
- polymyositis
- younger patients
- female preponderance
- detailed and: dry eyes/mouth, Raynauds, joint pain/swelling, rashes
- bloods: antinuclear antibodies, rheumatoid factor
- management: lipase with rheumatology, treat underlying disease
what is the summary diagnosis of ILD?
- clinical assessment: CTD symptoms, drugs, exposures
- bloods: antinuclear antibodies, rheumatoid factor, angiotensin-converting enzyme (ACE)
- spirometry/lung function: FVC, FEV/FVC ratio, gas transfer
- CXR: reticular shadowing
- HRCT pattern of disease: the cornerstone of diagnosis
- lung biopsy: enhances diagnosis but rik often outweighs benefit, may differentiate IPF from other potentially reversible causes
what is the summary treatment for ILD?
- remove cause
- immunosupression
- anti-fibrotics for IPF
what is sarcoid?
- multisystem granulomatous disorder
- non-necrotising granulomas
- cause unknown: 3 x more common in afro-carribeans, more severe disease, some familial clusters
- disease of the young: 75% of causes aged 30-60
- unpredictable clinical course
what is the histology of sarcoidosis?
- characterised by granulomatous 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
what are the most common areas that sarcoidosis affects?
- chest
- skin
- eyes
- lymph node biopsy
- hypercalcaemia
- peripheral nerves
what are the characteristics of lofgen’s syndrome?
- erythema nodosum
- bilateral hilar lymphadenopathy
- arthralgia
- excellent prognosis
- usually self limiting
what are the symptoms of pulmonary sarcoidosis?
- may be asymptomatic
- cough
- dyspnoea with exertion
- chest tightness
- systemic symptoms: fatigue, sweats, weight loss, fevers, arthralgia
how do you diagnose pulmonary sarcoidosis?
- no single diagnostic test
- combination of clinical picture, exclusion of alternative diagnoses and ideally biopsy of affected tissue
- baseline tests: renal function, liver function, calcium, serum ACE, CXR, ECG
- serum angiotensin-converting enzyme (ACE)
- biopsy everything: skin, lymph nodes, blind endobronchial biopsies
what are the characteristics of serum angiotensin converting enzyme (ACE)?
- secreted by activated alveolar macrophages in granulomas
- low sensitivity, poor specificity
- polymorphisms in ACE gene —> variation in peripheral blood ACE levels
- no correlation with CXR stage of disease
how do you treat pulmonary sarcoidosis?
major organ involvement
- ocular disease not responding to topical treatment
- cardiac
- neurological
less clear cut for 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
corticosteroids for 6-24 months are mainstay
- inhaled corticosteroids may provide symptomatic benefit
- additional immunosuppressants
what is obstructive spirometry?
- indicated the problem in the airways
- useful diagnostic
- reversible airflow obstruction
- fixed airflow obstruction in a smoker
- only a few other diseases of the airways
what is restrictive spirometry?
- indicated there is a problem
- not useful diagnostically
- useful for monitoring change
- severity indicator for ILD
- treatment criteria for IPF
when do you use restrictive spirometry of ILD?
- restriction of lung expansion of loss of lung volume
- directly measured by TLC: required lung function lab
- FVC reflects the TLC
- can be done in clinic
- useful for disease monitoring
