6 Patterns > Fibrosis Pattern > Additional Features > w/ Variable Involvement > Other Variable Fibrosis Diseases > Fibrotic IgG4 Disease

Fibrotic IgG4 Disease

Usual Interstitial Pneumonia (UIP) is the pattern of fibrosis classically described as having geographic and temporal variability.   Geographic variability means there are some areas of advanced scarring while other areas are completely normal.  Temporal variability refers to the presence of both old fibrosis (advanced scar) and new fibrosis (fibroblast foci).

SEE BELOW FOR SAMPLE SIGNOUT

If you are considering a diagnosis of UIP, the biopsy should show the following features:

• Advanced pulmonary fibrosis with architectural distortion of the lung
• Areas of normal lung
• Fibroblast foci
• Sharp demarcations between the advanced fibrosis and normal lung
• Fibrosis should be subpleural and paraseptal in its distribuition, creating "donuts" of fibrosis and "windows" of spared lung.

Advanced pulmonary fibrosis with architectural distortion of the lung

Fibroblast foci

Subpleural and paraseptal with "donuts" of fibrosis and "windows" of spared lung

Areas of normal lung/alveolar walls

Sharp demarcations between the advanced fibrosis and normal lung

Biopsies with the following features should NOT be called UIP:

• Cellular interstitial inflammation (consider CTD)
• Pleuritis (consider CTD)
• Lymphoid follicles (consider CTD)
• Numerous giant cells, especially if in the interstitium (consider chronic HP)
• Granulomas (consider chronic HP or Sarcoid)
• Abundant dust and inhalational debris (consider pneumoconiosis

Clinical Presentation

• UIP of IPF is a disease of older patients (typically greater than 60)
• UIP is much more common in men than women (3 to 1)
• Patients present with slowly worsening SOB and caugh
• Patients often have a smoking history
• There should be no history of autoimmune disease, exposure to organic antigens or occupational exposure

Radiology

• Peripheral and subpleural predominant reticulation
• Lower lobes more involved than upper lobes
• Honeycomb cyst formation
• GGO should be absent
• No air trapping should be present

Sample Signout

If you are comfortable that the biopsy has all the features of UIP and lacks the features arguing for an alternative explanation for the pulmonary fibrosis, consider the following approach to signing the case out:

Usual interstitial pneumonia pattern of pulmonary fibrosis (see comment)

Comment:  UIP pattern pulmonary fibrosis is seen most often in the setting of the clinical syndrome idiopathic pulmonary fibrosis (IPF).  However, even the perfect histologic UIP pattern may also be seen in advanced pulmonary fibrosis related to CTD, chronic HP, and pneumoconiosis.  Correlation with the clinical history and radiographic imaging studies should help confirm the diagnosis.

If there are some features missing, or some subtle features present that shouldn't be, consider the following approach:

Probable (or possible) usual interstitial pneumonia pattern of pulmonary fibrosis (see comment)

Comment:  Although there are some features of the UIP pattern in this case, ______ features are missing and there is the presence of ______ features that make a definitive diagnosis of UIP difficult.  Correlation with the clinical history and radiographic imaging studies may help clarify the diagnosis.