Restrictive: Hypersensitivity Pneumonitis

Question 1

What is HP?

Answer 1

Granulomatous reaction to inhaled organic antigens from environment (e.g. pigeon breeders lung)

Often seen in farmers and those exposed to birds

Question 2

What is hypersensitivity pneumonitis also known as?

Answer 2

Extrinsic Allergic Alveolitis

Question 3

Explain the pathophysiology of HP

Answer 3

Type IV hypersensitivity reaction

You see granulomas with eosinophils

Repeated exposure to antigen - leads to acute neutrophilic and mononuclear alveolitis

Fibrosis with bronchiolar obliteration occurs with continued exposure.

Question 4

List the signs and symptoms

Answer 4

• Fever
• Cough
• Dyspnoea hours after exposure
• Chest tightness
• Headache
• Reversible in early stage with removal of exposure
• But chronic exposure leads to interstitial fibrosis

In advanced cases, pulmonary fibrosis causes symptoms and signs of right heart failure, respiratory failure, or both

Question 5

Diagnosis?

Answer 5

CXR:

• Reticular or nodular opacities
• Seen in UPPER lobes
• Reduced lung volume
• Honeycombing

Question 6

Treatment?

Answer 6

Corticosteroids

Usually prednisone