Idiopathic Pulmonary Fibrosis
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Introduction
Idiopathic pulmonary fibrosis (IPF), or usual interstitial pneumonitis/pneumonia, is characterized by primarily wall changes. It is the most common idiopathic.
Incidence 10.7 m, 7.4 f /100,000
onset is usually by age 50.
The Case of...
a simple case introducing clincial presentation and calling for a differential diagnosis to get students thinking.
Causes and Risk Factors
Interstitial pulmonary fibrosis can be caused by many factors, including:
- drugs
- collagen vascular diseases
- radiation
- pneumonia
- exposure to occupational irritants
1.6-2.3x excess risk in smokers .
IPF most commonly affects people between 40-70.
Pathophysiology
Many interstitial pneumonias have identified causes, while others do not.
Types include:
- usual interstitial pneumonia (UIP)
- desquamative interstitial pneumonia (DIP)
- acute interstitial pneumonia (AIP)
- nonspecific interstitial pneumonia (NSIP)
- cryptogenic organizing penumonia (COP)
UIP reveals patchy involvement, particularly in the periphery. Repeated cycles of alveolitis by unknown agents lead to wound healing, fibroblastic proliferation, and fibrosis. Mediators such as TGF-beta are involved.
Dense fibrosis results, and remodeling of the lung architecture, leads to honeycombing.
A TH2 inflammatory response is involved, and IL-4, IL-13, eosinophils, and mast cells are all present.
Signs and Symptoms
- history
- physical exam
History
Idiopathic pulmonary fibrosis can present with insidious onset of dyspnea and nonproductive cough, with some symptoms occurring for months or years before definitive evaluation.
Physical Exam
Physical exam can reveal non-specific signs, including rapid shallow breaths, late inspiratory velcro-type fine basilar crackles, and clubbing.
Investigations
- lab investigations
- diagnostic imaging
Lab Investigations
Histological demonstration of fibroblastic foci are required, but may also be present in other diseases such as collagen vascular disorders and asbestosis.
Diagnostic Imaging
Pulmonary function testing can show restrictive changes, with reduced DLCO, FEF, and widened alveolar-arterial pressures.
CT can show honeycombing.
Differential Diagnosis
Treatments
Steroids can be used
Consequences and Course
Depending on the pattern of interstitial pneumonia, mortality ranges from 10-70%.
Median length of survival from diagnosis is 2.5-3.5 years.
Usual interstitial pneumonia has poor recovery; improvements in lung function is rare.
Resources and References
Khalil N and O'Connor R. 2004. Idiopathic pulmonary fibrosis: current understanding of the pathogenesis and the status of treatment. CMAJ. 171(2).
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