6. Hypersensitivity Pneumonitis

What etiology does this fall under?

KNOWN

Hypersensitivity pneumonitis defintion

hypersensitivity reaction affecting the lung parenchyma that occurs in response to inhaled organic dusts

What type of reaction is this?

• Type 3(III) or Type 4 (IV)

  • AKA extrinsic allergic alveolitis

What is a Type 3 reaction?

Immune complex (Antibodies)

• IgG & IgM

What is type 4 reaction?

T cells

What are some organic exposures?

• moldy hay

• grains

• bird droppings/feathers

• animal pelts

• coffee beans

• fish meal

• silage

• wood dust

• fungal or bacterial

Patho of Hypersensitivity pneumonitis

1. Inhale the antigen

2. alveolar walls are thickened & infiltrated with lymphocytes, plasma cells, eosinophils

3. immune reactions both type 3 and type 4

4. granulomas form in affected areas

5. small bronchioles are usually affected

6. may be exudate in the lumen

7. fibrotic changes occur in advanced cases of prolonged exposure

Acute clinical manifestations

• 4-6 hours after exposure & continue for 24-48 hours

Assessment:

• dyspnea

• fever

• shivering

• cough

• body ache

**Flu like symptoms

How will a PFT look for acute pts?

• Normal

  • some restriction during acute but lung function should return to normal shortly afterwards

How will CXR look for acute pts

Normal

What will we see on assessment of a chronic pt?

• dyspnea

• often with productive cough

• clubbing

• weight loss

• fatigue

What will we see on CXR for chronic pts?

Fibrosis of Upper lobes

What will PFTs look like for chronic pts?

Restrictive pattern

• decreased volume

• decreased CL

• decreased DLCO

How will ABG look for these pts

• hypoxemia (worse on exercise)

• normal or high PaCO2

  • as fibrosis contiues will see Comp resp acidosis

What will lab finings look like for these pts?

• abnormal serum proteins & presence of certain antibodies

• Presence of CD8 & lymphocytes (BAL)

How do we diagnose for Hypersensitivity pneumonitis

• history of exposure

• serum antibody test (looking for certain antibodies)

• CXR (look for fibrotic areas)

• Bronchoscopy (BAL) rule out other conditions or look at immune cells

• CT

How do we diagnose for Hypersensitivity pneumonitis

Provocation challenge

• intentional exposure to antigen

• followed by PFTs

Treatment for Hypersensitivity pneumonitis ?

1. Avoid exposure to pathogenic agents

• no treatment in mild cases

2. Corticosteroids for symptomatic relief

3. Bronchodilators if necessary

4. Pulmonary Rehab

What is the relationship with smokers and Hypersensitivity pneumonitis?

• Tend to exhibit symptoms less often

• But when it does occur in smokers - presentation is longer lasting