interstitial lung diseases

Question 1

what is the interstitium?

Answer 1

supporting structures of the lungs: alveolar endothelium, capillary endothelium, basement membrane, connective tissue

Question 2

what thickens the interstitium?

Answer 2

fluid, cells and fibrosis

Question 3

what are the functions of the extracellular matrix?

Answer 3

• tensile strength/elasticity
• low resistance for effective gas exchange
• tissue repair/modelling

Question 4

what happens to the extracellular matrix during fibrosis?

Answer 4

aberrant wound healing leads to excessive deposition in the interstitium

Question 5

what are the simple classifications of interstitial lung diseases?

Answer 5

• idiopathic
• sarcoidosis
• connective tissue disease
• hypersensitivity pneumonitis
• drugs

Question 6

what are the symptoms and clinical signs of IPF?

Answer 6

• slow progressive exertional dyspnoea
• non-productive cough
• dry, inspiratory bibasal velcro crackles
• +/- clubbing of fingers
• abnormal pulmonary function test results: restriction impaired gas exchange

Question 7

what is the summary of IPF?

Answer 7

• 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

Question 8

how do you manage IPF?

Answer 8

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

Question 9

how do you get hypersensitivity pneumonitis?

Answer 9

• bird droppings
• farmers lungs
• aspergillus
• antigen is unknown 50%

Question 10

what is hypersensitivity pneumonitis?

Answer 10

• diffuse inflammation of parenchyma in response to inhaled antigen
• tends to involve upper lobes

Question 11

how does acute hypersensitivity pneumonitis present?

Answer 11

• dyspnoea, cough, fever, malaise, crackles within 4-6 hours of heavy exposure
• often misdiagnosed as an infection

Question 12

how does subacute hypersensitivity pneumonitis present?

Answer 12

gradual onset of symptoms, weight loss is common

Question 13

how does chronic hypersensitivity pneumonitis present?

Answer 13

• insidious onset, history of acute episodes may be absent
• incomplete resolution with removal of antigen
• may lead to irreversible fibrosis

Question 14

how do you diagnose hypersensitivity pneumonitis?

Answer 14

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

Question 15

how do you manage hypersensitivity pneumonitis?

Answer 15

• avoidance of inciting antigen
• usually steroid-responsive in early disease
• may be progress to irreversible fibrosis

Question 16

what are the characteristics of drug induced ILD?

Answer 16

• 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

Question 17

what are the characteristics of connective tissue disease related ILD?

Answer 17

• 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

Question 18

what is the summary diagnosis of ILD?

Answer 18

• 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

Question 19

what is the summary treatment for ILD?

Answer 19

• remove cause
• immunosupression
• anti-fibrotics for IPF

Question 20

what is sarcoid?

Answer 20

• 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

Question 21

what is the histology of sarcoidosis?

Answer 21

• 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

Question 22

what are the most common areas that sarcoidosis affects?

Answer 22

• chest
• skin
• eyes
• lymph node biopsy
• hypercalcaemia
• peripheral nerves

Question 23

what are the characteristics of lofgen’s syndrome?

Answer 23

• erythema nodosum
• bilateral hilar lymphadenopathy
• arthralgia
• excellent prognosis
• usually self limiting

Question 24

what are the symptoms of pulmonary sarcoidosis?

Answer 24

• may be asymptomatic
• cough
• dyspnoea with exertion
• chest tightness
• systemic symptoms: fatigue, sweats, weight loss, fevers, arthralgia

Question 25

how do you diagnose pulmonary sarcoidosis?

Answer 25

• 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

Question 26

what are the characteristics of serum angiotensin converting enzyme (ACE)?

Answer 26

• 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

Question 27

how do you treat pulmonary sarcoidosis?

Answer 27

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

Question 28

what is obstructive spirometry?

Answer 28

• 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

Question 29

what is restrictive spirometry?

Answer 29

• indicated there is a problem
• not useful diagnostically
• useful for monitoring change
• severity indicator for ILD
• treatment criteria for IPF

Question 30

when do you use restrictive spirometry of ILD?

Answer 30

• 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