Interstitial Lung Disease

Question 0

What are the general effects of interstitial lung disease? What signs and symptoms does this cause?

Answer 0

Stiff, thickened lungs:
Reduced ventilation
Increased diffusion distance (hypercapnia and hypoxia)
Reduced perfusion

• reduced chest wall movement
• diffuse bilateral crackles
• shortness of breath
• cough (?inflammation)

Other signs & symptoms associated with underlying disease e.g.

• clubbing
• right heart failure
• tachypnoea
• cyanosis
• tachycardia

Question 1

Define interstitial lung disease. What does the interstitium refer to?

Answer 1

Diffuse parenchymal lung disease

Group of lung diseases affecting the interstitium (tissues & space around the alveoli; does not include epithelial or immune cells)

Interstitium includes: acini, alveoli lumen, bronchiolar lumen, bronchioles

Functions:

• diffusion pathway
• structure of lungs
• role in lung repair e.g. after infection, pollution, allergies etc.

Question 2

What are some of the different categories of causes of interstitial lung disease?

Answer 2

IDIOPATHIC (majority):
Various causes, diagnosis based on histological presentation
-> idiopathic interstitial pneumonitis (treat with steroids)

OCCUPATIONAL:

• asbestosis (teaching, plumbers, electricians, builders, telephone operators)
• silicosis
• coal worker’s pneumoconiosis

IATROGENIC: (rare - withdraw drug/give steroids)

• radiation
• methotrexate (rheumatoid arthritis)
• bleomycin (lymphoma)
• nitrofurantoin (UTIs)
• amiodarone (Wolff-Parkinson White, AF)
• chemotherapy

AUTOIMMUNE (connective tissue disorders):

• rheumatoid arthritis
• SLE
• polymyositis
• scleroderma
• Sjögren’s

IMMUNE:

• sarcoidosis
• hypersensitivity pneumonitis e.g. pigeon’s fancier’s disease

Question 3

What diseases can asbestos exposure cause?

Answer 3

Asbestosis = interstitial lung disease

Benign asbestos pleural effusions (BAPE)

Mesothelioma = tumour of pleura, peritoneum, or pericardium

Bronchogenic lung cancer

Rounded atelectasis

Question 4

What is sarcoidosis? How is it diagnosed and treated?

Answer 4

Multisystem granulomatous disorder causing various symptoms

• asymptomatic
• skin/eye lesions
• pulmonary infiltration
• bilateral hilar lymphadenopathy
• restrictive and obstructive lung effects

Differentials: TB, lymphoma

Presents in young adults or in 60s/70s

Biopsy transbronchial caseating granuloma

Treatment: observation v.s. prednisolone

Question 5

What are the different layers of the chest and pleura?

Answer 5

LUNG 
visceral pleura 
parietal pleura 
FAT PAD 
endothoracic fascia 
INNERMOST INTERCOSTAL MUSCLE
INTERCOSTAL FAT + VESSELS 
INTERCOSTAL MUSCLES

Question 6

What are some of the functions of pleura?

Answer 6

Couples chest wall and lung movement (inward lung recoil & outward chest wall recoil)

Pleural fluid circulation:

• pleural fluid produced by parietal pleura only (Starling’s law of capillaries)
• pleural fluid absorbed via parietal pleural lymphatics
• ~15ml/day (but can increase)

Question 7

What are some of the causes of pleural fluid accumulation? How can this be immediately treated?

Answer 7

INCREASED PRODUCTION:
Increased lung interstitial fluid/hydrostatic pressure/permeability
Reduced oncotic pressure

• heart failure
• peritoneal dialysis
• hypoalbuminaemia
• cirrhosis
• nephrotic syndrome

DECREASED ABSORPTION:
Lymphatic blockage/increased systemic venous pressure

• heart failure
• SVC obstruction

Drain via thoracocentesis

Question 8

What are the different types of pleural effusion?

Answer 8

Transudate (increased hydrostatic pressure/reduced oncotic pressure)

Exudate - proteins/LDH (increased permeability - infection/malignancy)

Empyema - pus in pleural cavity (most commonly due to pneumonia)

Haemothorax

Chylothorax (lymph in pleural cavity)

Question 9

What are some different types of pleural malignancy?

Answer 9

Primary = mesothelioma (asbestos exposure) -> pain, breathlessness

Metastatic

Question 10

Give some examples of chest wall disease. What signs and symptoms do these cause?

Answer 10

CONGENITAL:

• pectus deformities
• scoliosis
• kyphosis
• muscular dystrophy

ACQUIRED:

• trauma
• iatrogenic e.g. thoracoplasty (lung removed to treat TB)
• ankylosing spondylitis
• motor neurone disease

Signs & symptoms:

• reduced ventilation
• sleep disordered breathing
• poor clearance of secretions
• atelectasis
• pneumonia