Extrinsic allergic alveolitis Flashcards

1
Q

What is extrinsic allergic alveolitis?

A

interstitial inflammatory disease of the distal gas-exchanging parts of the lung caused by inhalation of organic/antigenic dusts.

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2
Q

What is extrinsic allergic alveolitis also known as?

A

hypersensitivity pneumonitis (HP).

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3
Q

What is the aetiology of extrinsic allergic alveolitis?

A

In sensitised individuals, repetitive inhalation of allergens provokes a hypersensitivity reaction which varies in intensity + clinical course depending on the antigen.
In the acute phase, the alveoli are infiltrated with acute inflammatory cells.
Antigenic dusts include microbes + animal proteins

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4
Q

Give examples of extrinsic allergic alveolitis

A

Farmer’s Lung: mouldy hay containing thermophilic actinomycetes
Pigeon Fancier’s Lung: blood on bird feathers + excreta
Maltworker’s Lung: barley or maltlings containing Aspergillus clavatus
Bagassosis or sugar worker’s lung (Thermoactinomyces sacchari)

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5
Q

Describe the epidemiology of extrinsic allergic alveolitis

A

UNCOMMON
2% of occupational lung disease
50% of reported cases affect farm workers
Geographical variation

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6
Q

List 6 symptoms of acute extrinsic allergic alveolitis

A
REVERSIBLE episodes of:  
Dry cough   
Dyspnoea  
Malaise   
Fever  
Myalgia  
Wheeze + productive cough may develop if repeat high-level exposure
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7
Q

List 4 symptoms of chronic extrinsic allergic alveolitis

A

Slowly increasing breathlessness
Decreased exercise tolerance
Weight loss
Exposure is usually chronic, low-level + there may be no hx of previous acute episodes

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8
Q

Give 3 signs of acute extrinsic allergic alveolitis

A

Rapid shallow breathing
Pyrexia
Inspiratory crackles: Bi-basal rales (crackles at base of lungs, present during acute HP but not between episodes

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9
Q

Give 2 signs of chronic extrinsic allergic alveolitis

A

Diffuse fine inspiratory crackles (rales)

Clubbing (rare)

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10
Q

What bloods should be taken in extrinsic allergic alveolitis?

A

FBC: neutrophilia, lymphopenia, high ESR, normocytic normochromic anaemia
ABG: reduced PO2 + PCO2
Albumin may be low: but non-specific

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11
Q

What investigations are performed for extrinsic allergic alveolitis?

A
Bloods
ABG
CXR
High Resolution CT-Thorax  
Pulmonary Function Tests  
Diffusing lung capacity of carbon monoxide
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12
Q

Why perform serology for extrinsic allergic alveolitis?

A

Test for IgG to fungal or avian antigens

not diagnostic as may find in normal individuals

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13
Q

What may be seen on CXR in extrinsic allergic alveolitis?

A

Often NORMAL in acute episodes
Acute: fibrosis, upper zone mottling/ consolidation
Hilar lymphadenopathy in rare cases
Chronic: upper zone fibrosis, honeycomb lung

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14
Q

What may be seen on high resolution CT in extrinsic allergic alveolitis?

A

Detects early changes
Chronic: Patchy ‘ground glass’ shadowing + nodules, extensive fibrosis
Used in chronic HP to confirm dx

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15
Q

What may be seen on pulmonary function tests in extrinsic allergic alveolitis?

A

ACUTE: restrictive pattern (low FEV1, low FVC)

SUBACUTE/ CHRONIC: obstructive + restrictive pattern

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16
Q

What is seen on Diffusing lung capacity of carbon monoxide in extrinsic allergic alveolitis?

A

Decreased

may be normal in between episodes of acute

17
Q

Describe disease progression in extrinsic allergic alveolitis

A

Early dx + prompt allergen removal can halt + reverse disease progression, so prognosis can be good.
With chronic exposure, granuloma formation + obliterative bronchiolitis.

18
Q

When do symptoms start in acute extrinsic allergic alveolitis?

A

4-12 hrs after exposure