Interstitial Lung disease

Question 1

Pathophysiology of interstitial lung disease?

Answer 1

(1. ) Gas exchange takes place at the interstitium
(2. ) Anything that interferes with that (e.g. oedema, fibrosis) causes a reduction in elasticity of lungs [restrictive].
(3. ) This causes increases stiffness, decreases compliance and changes in PFTs
(4. ) Ix would show reduced TCO, VC, FEV1 although relatively normal FEV1/FVC and PEFR.

Question 2

What is Acute Respiratory Distress Syndrome (ARD)?

Answer 2

(1. ) Inflammation of lungs that leads to non-cardiogenic pulmonary oedema. Main site of injury is to alveolar-capillary mb.
(2. ) It is not a primary lung disease, it is a complication of systemic insult that causes widespread inflammation + damage to lungs
(3. ) Acute ILD is an ARD

Question 3

What causes ARD?

Answer 3

(1. ) This can be caused by direct injury to the lung tissue by:
- drugs and toxin reactions
- gastric aspiration
- sepsis: pneumonia, UTI
- radiation for cancers
- diffuse intrapulmonary haemorrhage

-> which causes thickening of intersitium and loss of resp function

Question 4

Clinical features or ARD

Answer 4

• Cyanosis
• Tachypnoea
• Peripheral vasodilation
• Pulmonary oedema
• Bilateral fine crackles
• Low oxygen saturation

Question 5

Ix + Dx Criteria for ARD (4)

Answer 5

1. Sx developed within 1w of suspected insult
2. CXR shows bilateral opacities
3. Sx are not fully explained by congestive HF
4. low PaO2:FiO2 (arterial:inspired O2) < 300mmHg

Ix

• CXR, ABG, sputum + blood cultures
• consider BNP + ECG

Question 6

What is Idiopathic Pulmonary Fibrosis, IPF? RF?

Answer 6

(1. ) Progressive fibrosing interstitial pneumonia of unknown cause.
(2. ) Restrictive pattern of PFT: stiff lungs, drop in oxygen level
(3. ) Complications: Cor pulmonale or RSHF due to hypoxemia
(4. ) RF = smoking, fx, Males, >50y

Question 7

Pathology of IPF

Answer 7

(1. ) IPF causes scarring of lung tissue in later life, by the following:
(a. ) Fibroblasts (repair damaged tissue) migrate to lungs to become myofibroblasts.
(b. ) These deposit collagen and in IPF they are resistant to apoptosis + proliferate + form fibroblast foci (collection of fibroblasts).
(c. ) This causes thickened tissue that leads to lower gas exchange efficiency

Question 8

Clinical Features of IPF

Answer 8

• ASx, usually found incidentally on CT
• Progressive breathlessness
• Non-productive cough
• Ex may reveal signs: bilateral crackles, clubbing, cyanosis

Question 9

DX and IX of IPF

Answer 9

Dx = where there is confidence in Hx + PFT + imaging biopsy is not needed h/e if not a biopsy is indicated.

Ix

(1. ) PFT: Spirometry + CO gas transfer
- Restrictive pattern - reduced lung volume
- Decreased DLCO

(2. ) Imaging: CXR, HR-CT
- both will show dec lung vol, CT will show histology

(3.) Bronchoalveolar lavage and/ or transbronchial biopsy. Note: biopsy may not be done

Question 10

(5) Histology pattern of IPF

Answer 10

(1. ) usual intestinal pneumonia (UIP)
(2. ) honeycombing (destruction of alveoli) and thickening of alveoli
(3. ) Peripheries and base of the lung - ‘subplural regions’
(4. ) Fibroblast foci (collection of fibroblasts)
(5. ) Spatial heterogeneity (normal lung tissue next to abnormal tissue)

Question 11

Mx and Tx of IPF

Answer 11

Medial survival of 2-5y from dx

1. Supportive Care
2. Pulmonary rehabilitation
3. Consider lung transplant
4. Medical Interventions: Slows down progression of disease + improves FVC
   - Pirfenidone: SE = photosensitivity
   - b. Nintedanib: SE = diarrhoea

Question 12

What is Hypersensitivity Pneumonitis (HP)/Extrinsic allergic alveolitis (EAA)? Key allergens associated with these?

Answer 12

(1. ) Inflammation of the alveoli and distal bronchioles causes by an immune response to inhaled allergen.
(2. ) This is a type III hypersensitivity reaction i.e. immune complex (Antigen + antibody) deposition in lungs, which either resolves or leads to fibrosis.

(3. ) Allergens:
- Occupational exposure to organic dust, chemicals etc
- Animals, avian protein antigen
- Key types = Bird’s fancier’s lung, farmer’s lung caused by fungus

Question 13

Clinical features of Hypersensitivity Pneumonitis

Answer 13

(1. ) Flu-like Sx accompanied by cough, wheeze, breathlessness when exposed to antigen
(2. ) Crackles and squeaks may be heard on auscultation
(3. ) Fever, chills, malaise
(4. ) Weight loss

Question 14

Ix of Hypersensitivity Pneumonitis

Answer 14

(1. ) Clinical history: look for tiggers- pets? Mould? Occupation?
(2. ) Analysis of antigen-specific IgG
(3. ) Imaging: CXR, HRCT

(4. ) PFT
- Spirometry will show restrictive pattern for acute h/e may be obstructive in chronic
- Reduced oxygen saturation
- Impaired CO gas transfer

(5. ) Bronchoalveolar lavage
- lymphocytes more predominant in airways
- Useful for distinguishing HP from other ILDs

(6.) Lung biopsy

Question 15

Mx of Hypersensitivity Pneumonitis

Answer 15

• Removal of antigen is KEY h/e identification of antigen is not always possible
• Steroid for acute/subacute disease
• Supplemented oxygen to treat hypoxemia

Question 16

5 Common culprits of drug induced ILD? Mx?

Answer 16

Clinical scenario will show an individual getting chesty every time after their medication

Common culprits:

• Nitrofurantoin
• Methotrexate
• Amiodarone
• Bleomycin
• Novel checkpoint inhibitors (cancer)

Tx
- removal of drug + do no rechallenge

Question 17

Ix for CTD-ILD

Answer 17

Individual may present with breathlessness as well as Sx of their CTD (e.g. Sclerosis)

(1. ) CXR = inflammatory ‘ground glass’ changes
(2. ) Anti Scl-70 (Anti-topoisomerase) +ve a risk factor for ILD

Question 18

What is Pneumoconiosis ?

Answer 18

(1. ) Permanent alteration of lung structure due to inhalation of mineral dust
(2. ) Inhaled particles accumulate around bronchioles and produce localised scarring. In some cases it can produce a blackening of lung tissues (anthracosis).
(3. ) Most important pneumonoconiosis = coal worker’s, silicosis, asbestosis