4- interstitial & occupational lung diseases Flashcards
what is interstitial disease?
- any disease affecting lung interstitium (alveoli themselves, deep in bronchial tree)
- interferes with gas transfer
what is result of interstitial disease on pulmonary function tests?
restrictive pattern (may have airway obstruction too)
what are the 4 different broad categories of ILD?
- group where we know the cause e.g. drug or associations
- idiopathic interstitial pneumonia = group of conditions e.g. IPF. get either inflammation or impaired mechanisms causing lung disease
- granulomatous ILDs e.g sarcoidosis
- other forms = random mix, most are rare
what is sarcoidosis?
- granulomatous (type 4 hypersensitivity) disease of unknown cause
- multi-system involvement
- non-caseating granuloma of unknown aetiology: probable infective agent in susceptible individual. Imbalance of immune system with excessive type 4 (cell mediated) hypersensitivity
→less common in smokers
what are presentations of acute sarcoidosis?
- painful nodules on shins of legs (erythema nodosum)
- bilateral hilar lymphadenopathy
- painful red eyes due to uveitis, fever
what are presentations of chronic sarcoidosis?
doesn’t settle without treatment, goes on for years - risk of lung scarring due to persistent inflammation leading to fibrosis. can get impaired calcium metabolism = hypercalcaemia, important to screen them for other organ involvements
= often presents in generic way with a lot of symptoms that can be other diseases so important to rule out things like TB, lymphoma, carcinoma, fungal infections
what are investigations for sarcoidosis?
- basic chest x-ray (shows enlarged lymph nodes)
- CT scan = gives more detail e.g scarring or lung involvement
- blood test = renal function, liver function, calcium levels, ACE levels (if high good marker for disease treating with), inflammatory markers
what is treatment for acute or chronic sarcoidosis?
acute = often self limiting and no treatment needed
chronic = treat with steroids and immunosuppression (azathioprine, methotrexate, anti-TNF treatment)
what is hypersensitivity bit of hypersensitivity pneumonitis?
type 3 hypersensitivity = immune complex deposition reaction. reaction to antigen lymphocytic alveolitis
complex deposited in lungs causing inflammation including type 3 + type 4 hypersensitivity
what are the causes of hypersensitivity pneumonitis?
things that cause hypersensitivity reaction like
- fungal stuff = Thermophilic actinomycetes (farmers lung, malt workers, mushroom workers, other moulds)
- avian antigens (bird fanciers lung)
- drugs (gold, bleomycin, sulphasalazine)
what is very important for diagnosis of hypersensitivity pneumonitis?
history = some seemingly random parts of social history can be very important (no cause is identified in 30% of HP cases)
what are some classical signs and symptoms of acute hypersensitivity pneumonitis?
acute:cough, breathless, fever, myalgia = classic symptoms come on several hours after exposure (not immediate like type 1). it’s alveolar problems so not wheezy (that’s airways disease)
signs = pyrexia, crackles, hypoxia (doesn’t usually have finger clubbing!)
what makes hypersensitivity pneumonitis chronic?
repeated low dose antigen exposure over years = progressive breathlessness + cough
what is treatment for acute hypersensitivity pneumonia?
- Treatment: oxygen, steroid and antigen avoidance = Antifibrotic therapy in cases of progressive fibrosis (Nintedanib)
what investigations do you do for hypersensitivity pneumonia?
- can do specific blood test (IgG for specific think you think causing)
- chest x-ray to check for pulmonary fibrosis (common in upper zone)
- pulmonary function test = shows restrictive defect
what is important takeaway point about IPF that differs from other ILDs?
NOT inflammatory! - it just involves fibrosis = pulmonary scarring with no inflammation, makes tricky to treat and
what are other differential diagnoses of pulmonary fibrosis? (to consider when diagnosing IPF)
- rheumatoid, SLE, systemic sclerosis, asbestos
- drugs with pulmonary fibrosis side effect - amiodarone, busulphan, bleomycin, penicillamine, nitrofurantoin, methotrexate
what are characteristic clinical signs of IPF?
fibrosis + finger clubbing = more likely to be IPF (as others don’t have finger clubbing)
- bilateral fine inspiratory crackles
what is found on on chest x-ray and CT scan of IPF?
- CxR - bilateral infiltrates;
- CT scan - reticulonodular fibrotic shadowing, worse at the lung bases, and periphery. Traction bronchiectasis (dilated and thickened bronchi). Honey-combing cystic changes. (clusters of advanced fibrosis)
is lung biopsy always necessary for IPF?
no, CT scan most important - if CT atypical then might do lung biopsy
what would a typical biopsy for IPF show?
Usual Interstitial Pneumonia pattern (UIP) heterogenous fibrosis in alveolar walls with fibroblastic foci and destruction of architecture causing honeycombing. Inflammation is minimal
what is the treatment for IPF?
tricky treatment as immunosuppressants + steroids don’t work as no inflammation
- there are some new antifibrotic drugs (pirfenidone + nintedanib) but they are very expensive with lots of side effects and don’t reverse fibrosis just slow progression
- if young enough can do lung transplant but most over 65 so hard diagnosis with only a few years to live
what is a complicated pneumoconiosis?
progressive massive fibrosis that would grow and engulf the lungs (rare but serious) = breathlessness
what lung diseases can asbestos cause?
pleural diseases = affecting pleura (layer)
- Benign pleural plaques - fibrosis of plaque = asymptomatic.from previosu asbestosis exposure
- Acute asbestos pleuritis - fever, pain, bloody pleural effusion
- Pleural Effusion and Diffuse pleural thickening - restrictive impairment = no treatment
- Malignant Mesothelioma - incurable pleural cancer. still fairly common. Presents with chest pain and pleural effusion. No available treatment - fatal within two years.
- pulmonary fibrosis = asbestosis
- bronchial carcinoma
what is defining difference between asbestosis and IPF?
asbestosis doesn’t develop as quickly as IPF
why is upper lobes commonly more affected than lower lobes in lung diseases?
upper lobe affected more than lower as inhalation disease (inhale more in upper lobes)
what are the 2 forms of asbestosis?
- Serpentine (curved) – relatively safe = Get stuck in upper airways and cleared
- Straight (amphibole) – highly dangerous = More aerodynamic – travel further into lung, penetrate epithelium and get into interstitium
- Once phagocytosed – induce inflammation and stimulate fibrosis
