Hypersensitivity pneumonitis (HP)

Question 1

Hypersensitivity pneumonitis (HP)?
- def
- b/ground

Answer 1

Def:
- Immunologically mediated
- Lung disease
- Resulting from repeated inhalation of
- Environmental or occupational
- Organic & non-organic
- Antigens

B/ground:
- Occur at any age, usu after 40
- Exposure to antigen may have ceased when Dx is made
- Auscultation of chest: insp crackles and/or high-pitch inspiratory squeaks
- Dx by exclusion of alternative cause and MDT
- Exposure likelihood:
identified, indeterminate or unidentified

Question 2

Hypersensitivity Pneumonitis
- radiological changes

Answer 2

Types:
1) Typical non-fibrotic
2) Compatible non-fibrotic
3) Typical fibrotic
4) Compatible non-fibrotic
5) Indeterminate fibrotic

Question 3

Hypersensitivity Pneumonitis
- radiological changes:
1) Typical non-fibrotic
2) Compatible non-fibrotic

Answer 3

1) Typical non-fibrotic:
i) Profuse centrilobular nodules
ii) GGO all lung zones
iii) Mosaicism
iv) Headcheese sign
v) No alternative Dx

2) Compatible non-fibrotic
i) Not profuse centrilobular nodules
ii) No mosaicism
iii) Patchy or diffuse GGO
iv) No alternative Dx

Question 4

Hypersensitivity Pneumonitis
- radiological changes:
3) Typical fibrotic
4) Compatible non-fibrotic

Answer 4

3) Typical fibrotic:
i) Fibrosis (reticular or GGO with traction bronchiectasis or bronchiolectasis, lobar volume loss, honeycombing)
ii) Profuse centrilobular nodules
iii) GGO opacities all lung zones
iv) Mosaicim with headcheese sign
v) No alternative Dx

4) Compatible non-fibrotic:
i) Patchy or diffuse GGO
ii) Patchy, non-profuse centrilobular nodules
iii) Mosaicism not meeting typical fibrotic HP
iv) No alternative Dx

Question 5

Histological findings in HP

Answer 5

1) BAL fluid:
- lymphocytosis (>30%) – useful and only needed if exposure Hx or HRCT indeterminate
- high cellular content
- activated T-lymphocytes
- usu predominance CD8 T-lymphocyte → decrease CD4/CD8 ratio

2) HPE:
Non-fibrotic:
1) small airway involvement,
2) uniform cellular interstitial inflammation that is
3) predominantly
lymphocytic, with
4) at least a single, poorly formed granuloma and/or multinucleated giant cell.

Fibrotic:
1) airway-centred fibrosis with or without widespread peribronchiolar metaplasia,
2) fibrosing interstitial pneumonia, which might have the appearance of fibrotic NSIP, UIP, isolated peribronchiolar fibrosis, or fibrotic lung disease that defies a specific classification, and
3) poorly formed granulomas.

Question 6

Rx of HP
- long term & acute flare

Answer 6

1) Antigen avoidance & disease education
2) Systemic steroid with tapering dose
- In severe Sx, acute exac +/- disease progression
3) Steroid sparing: Aza, MMF
4) Ax steroid complications: DM, HTN, cataract, OP
5) Adjunctive:
- LTOT, pulm rehab, smoking cessation, vax
6) Rx comorbids: COPD, OSA, GORD, Pulm HTN, obesity, CAD, Ca
(mnemonic: COG PO CaCa)
7) Lung transplant (early referral)
8) Pall care, inc Sx Mx (e.g. cough) – e.g. morphine
9) Acute flare:
Given T pred 20mg for 2w, then T pred 15mg for 2w, then T pred 10mg for 6-8w (until MMF available).
MMF is used for fibrotic disease
Azathioprine used in inflammation disease
10) consider Nintedanib if PPF
(INBUILD trial: Nintedanib slows down FVC decline/ acute exac & mortality in PPF vs placebo)

Question 7

Monitoring for HP

Answer 7

1) Surveillance for allergen avoidance
2) Physiological (Spiro/DLCO/6MWT), HRCT & Sx monitoring every 3-6m or sooner if Sx
3) Ax drug toxicity
4) Ax & Mx comorbidities

Question 8

Side effects of commonly given Rx in ILD

Answer 8

Question 9

Risk factors for mortality in HP

Answer 9

Question 10

Diagnostic algorithm for HP

Answer 10

1) Exposure to inciting antigen
2) HRCT
3) BAL
4) MDT
5) +/- Lung Bx