Pathology of restrictive lung disease Flashcards
What is the lung interstitium?
Pulmonary interstitium is a collection of support tissues within the lung that includes the alveolar epithelium, pulmonary capillary endothelium, basement membrane, perivascular and perilymphatic tissues, which acts to form an airtight barrier
What happens in interstitial lung disease?
Normal alveolar walls become widened and thickened due to a pathological process leading to the formation of stiff, non-compliant lungs
What is the majority of the interstitium made up of?
Elastin - what is affected in interstitial lung disease
How does restrictive lung disease affect the spirometry values of the patient?
Both FEV1 and FVC are decreased, but the ratio is maintained at “healthy” 0.8 (80%)
What causes the reduced gas transfer in restrictive lung disease?
Seperation of capillary and alveolar epithelium
Increased diffusion distances in fibrosis
What is associated with diffuse alveolar damage?
Major trauma Chemical injury/toxic inhalation Circulatory shock Drugs Infection AI disease Radiation ARDS Can be idiopathic
Describe the key characteristics of diffuse alveolar damage
Marked changes in blood pressure
Hyaline membrane production around alveoli
Accumulation of exudate in alveoli
Pulmonary oedema
Describe the histological features of diffuse alveolar damage
Protein rich oedema Fibrin Hyaline membranes around alveoli Denuded basement membrane Epithelial + fibroblast proliferation Fibrous scarring of tissue
Describe sarcoidosis
Multisystem granulomatous disease causing epitheliod and multinucleate giant cell granulomas, where necrosis or caseation is unusual
What group is most associated with sarcoidosis?
Young females, northern europeans or afro-caribeans
What organs are usually affected in sarcoidosis?
Lungs Spleen Liver Skin Eyes Skeletal muscle Bone marrow Salivary glands
How do those with sarcoidosis usually present?
Painful joints Erythema nodosum (tender red bumps) Bilateral hilar lymphadenopathy Abnormal CXR SOB Cough
Describe some blood results typical of sarcoidosis
Increased calcium
Normal PTH
Increased ACE
What is the Kveim test?
Test for sarcoidosis - inject cells from liver of sarcoidosis patient into skin, if they develop a granuloma at the site they are positive for sarcoidosis
How can we rule out TB in sarcoidosis?
If tissue is necrotic
Tuberculin/mantoux test
Kveim test
What is hypersensitivity pneumonitis?
Inflammation of the alveoli caused by type III or IV hypersensitivity reactions to inhaled organic dusts
Where is the main site of reaction in hypersensitivity pneumonitis?
Hilar regions, where the inhaled agents are usually deposited
What are some common antigens which cause hypersensitivity pneumonitis?
Thermophilic actinomycetes (mould hay) Micropolyspora faeni Thermactinomyces vulgaris Bird/animal proteins Fungi Chemicals
Describe the symptoms of acute hypersensitivity pneumonitis
Fever Dry cough Myalgia Crackles on inspiration Tachypnoea Wheeze Precipitating antibody
Describe the symptoms of chronic hypersensitivity pneumonitis
Malaise SOB Cough Low grade illness Crackles on inspiration Some wheeze Can lead to respiratory failure Cyanosis Finger clubbing
Describe the histopathology of hypersensitivity pneumonitis
Evidence of diffuse chronic inflammation Soft centriacinar granulomata Bilateral Interstitial pneumonitis Alveolar septal thickening (infiltrates) Foamy histiocytes
Describe usual interstitial pneumonitis
Patchy interstitial chronic inflammation, resulting in type II pneumocyte hyperplasia and smooth muscle and vascular proliferation due to some sort of injury. Results in honeycomb lung and cobblestoning
What can cause usual interstitial pneumonitis?
Connective tissue diseases
Drug reactions
Post infection
Industrial exposure
Most cases are cryptogenic or idiopathic and are therefore called either:
- cryogenic fibrosing alveolitis
- idiopathic pulmonary fibrosis
Describe the typical usual interstitial pneumonitis patient
Elderly male
Poor prognosis
What are the symptoms of usual interstitial pneumonitis?
Dyspnoea Cough Basal crackle Cyanosis Clubbing
What can be seen on CXR of usual interstitial pneumonitis?
Basal/posterior disease
Diffuse infiltrates
Cysts
Ground glass opacities
