Other interstitial pneumonitis / fibrosis

Desquamative interstitial pneumonitis

Editor-in-Chief: Debra L. Zynger, M.D.
Akira Yoshikawa, M.D.
Andrey Bychkov, M.D., Ph.D.

Topic Completed: 1 March 2018

Minor changes: 10 May 2021

Copyright: 2003-2022,, Inc.

PubMed Search: Desquamative interstitial pneumonitis [title]

Akira Yoshikawa, M.D.
Andrey Bychkov, M.D., Ph.D.
Page views in 2021: 3,892
Page views in 2022 to date: 163
Cite this page: Yoshikawa A. Desquamative interstitial pneumonitis. website. Accessed January 21st, 2022.
Definition / general
  • In 1965, Liebow et al reported a series of cases with interstitial pneumonia characterized by massive proliferation and desquamation of epithelial cells and coined the term "desquamative interstitial pneumonia" (DIP) (Am J Med 1965;39:369)
  • In 1977, Tubbs et al determined, based on electron microscopy, that most cells within alveolar spaces were macrophages (Chest 1977;72:159)
  • In 2013, American Thoracic Society / European Respiratory Society (ATS / ERS) categorized DIP as a smoking related interstitial pneumonia, as well as respiratory bronchiolitis related interstitial lung disease (Am J Respir Crit Care Med 2002;165:277, Am J Respir Crit Care Med 2013;188:733)
Essential features
  • A rare but characteristic type of smoking related lung disease
  • Histologically, massive accumulation of intra-alveolar macrophages is the key finding
  • Although “desquamated cells” are now recognized as intra-alveolar macrophages and ATS / ERS once considered to change the name of this entity to “alveolar macrophage pneumonia”, it is still officially called “desquamative interstitial pneumonia” (Am J Respir Crit Care Med 2002;165:277)
ICD coding
  • Desquamative interstitial pneumonia: J84.117
  • Bilateral (or sometimes unilateral) lobes of the lung
  • Respiratory bronchiolitis, respiratory bronchiolitis associated interstitial lung disease (RB-ILD) and DIP are now considered on a spectrum and it can be difficult in some cases to separate these diseases clearly (Histopathology 2011;58:509)
    • Deaths are somewhat common in DIP (6 - 30%) but rare in respiratory bronchiolitis and RB-ILD
  • Studies with mouse models suggest a two hit development (Chest 2015;148:1307, Antiviral Res 2011;92:319)
    • Primary smoking exposure induces GM-CSF secretion from airway epithelial cells
    • Subsequent infection provokes macrophage activation and accumulation
Clinical features
  • Slight to mild chronic respiratory failure
    • Dyspnea on exertion
    • Dry cough
    • Digital clubbing
  • Abnormal chest auscultation
    • End inspiratory fine crackles in bibasilar lung
  • Mild systemic symptoms may accompany
    • Fever
    • Fatigue
    • Weight loss
  • Normal or slightly abnormal pulmonary function tests (restrictive, obstructive or mixed pattern)
    • Decreased forced vital capacity (FVC)
    • Decreased diffusing capacity of the lung for carbon monoxide (DLCO)
  • See details in review (Eur Respir Rev 2013;22:117, Histopathology 2011;58:509, Chest 2017;3692:33197)
  • Based on clinical features, radiology and histopathology (Am J Respir Crit Care Med 2002;165:277)
    • Lung biopsy is required to establish a firm diagnosis since the clinical and radiological findings are often not specific
    • However, a biopsy may not be necessary if the clinical and radiological features are suggestive enough (Radiology 1999;211:555)
  • Increased serum KL-6
Radiology description
  • Simple chest radiograph (Clin Radiol 2003;58:259)
    • Variable and nonspecific, including ground glass opacity and reticulonodular shadow
  • High resolution CT (Clin Radiol 2003;58:259, Chest 2017;3692:33197)
    • Bilateral and subpleural ground glass opacity
    • Middle to lower zones are affected predominantly; however, the upper zone can be involved
    • Linear shadow, cystic spaces, emphysema, traction bronchiectasis and honeycombing can be accompanied
Radiology images

Images hosted on other servers:
High resolution CT High resolution CT High resolution CT

High resolution CT

Prognostic factors
Case reports
Gross description
  • Diffuse bronchocentric multinodular change with lower lobe predominance
  • Firm and consolidated
  • Pale gray to white
  • Mild to moderate increase in weight of the lung
  • Honeycomb change can be seen but sparsely
Microscopic (histologic) description
  • Diffuse and massive accumulation of intra-alveolar macrophages (smoker's macrophages)
    • Brown pigments, more finely granular than hemosiderin, are seen in the eosinophilic cytoplasm (smoker's pigments)
    • Giant cells can be also seen
  • Mild to moderate interstitial fibrosis or cellular change
    • Diffuse and homogeneous involvement (similar to NSIP) along with alveolar macrophages
    • Lymphoid follicles and eosinophils are often present
    • Marked dense fibrosis, architectural distortion, fibroblastic focus or presence of intact alveolar walls in the area of accumulated macrophages should suggest another diagnosis
  • See details (Histopathology 2011;58:509, Chest 2017;3692:33197, Chest 2015;148:1307, Eur Respir Rev 2013;22:117)
Microscopic (histologic) images

Contributed by Akira Yoshikawa, M.D.
Low power

Low power

Middle power Middle power

Middle power

Smoker's macrophages Smoker's macrophages

Smoker's macrophages

Giant cells

Giant cells

Lymphoid follicles

Lymphoid follicles

Low power

Low power

Middle power Middle power

Middle power

Smoker's macrophages and interstitial fibrosis Smoker's macrophages and interstitial fibrosis Smoker's macrophages and interstitial fibrosis

Smoker's macrophages and interstitial fibrosis

Images hosted on other servers:
Trichrome staining

Trichrome staining

H&E and IHC of CD68

H&E and IHC of CD68

Virtual slides

Images hosted on other servers:
Dr. Rosai's collection<br>- Desquamative interstitial<br>pneumonitis

Dr. Rosai's collection
- Desquamative interstitial

Cytology description
  • Increased eosinophil or neutrophil ratio in bronchoalveolar lavage fluid
Positive stains
Electron microscopy images

Images hosted on other servers:
Numerous lysosomes in macrophages Numerous lysosomes in macrophages Numerous lysosomes in macrophages

Numerous lysosomes in macrophages


Histopathology Lung - Desquamative interstitial pneumonia

Differential diagnosis
  • Alveolar hemorrhage
    • Hemosiderin laden macrophages are seen
    • Hemosiderin is positive for Prussian blue but more coarse and larger
  • Eosinophilic pneumonia
    • Marked interstitial eosinophils and edema, organizing pneumonia, mucus plugs and fibrin deposition are seen
  • Hypersensitivity pneumonitis
    • Clinically, smoking history is less common
    • Patinets have a history of exposure to antigens such as spores of fungi, animal proteins and chemicals
    • Positive for serum antibody to causative antigens
    • Airway centered change, interstitial cellular infiltration and granuloma are seen
  • Nonspecific interstitial pneumonias
    • Accumulation of intra-alveolar macrophages may be seen but focal or mild (DIP-like reaction)
    • Clinically, patients with NSIP often associated with collagen tissue disease
  • Pneumoconiosis
    • Clinically, the patients usually have a history of occupational exposure
    • Macrophages, giant cells and causative particles (e.g. asbestos body, anthrosilicotic dust) are seen especially in interstitium
  • Pulmonary Langerhans cell histiocytosis
    • Bronchocentric nodules of Langerhans cells
    • Positive for CD1a, S100 and Langerin
  • Respiratory bronchiolitis
    • Most common lung disease in smokers
    • Clinical manifestation is slight or absent
    • Macrophage accumulation in bronchocentric predominance is seen on histology
    • Interstitial pneumonia, lymphoid follicles, giant cells and eosinophils are absent
  • Respiratory bronchiolitis-associated interstitial lung disease
    • Less common lung disease in smokers
    • Physical deterioration, including respiratory symptoms and abnormal pulmonary function, is significant enough to diagnose as interstitial lung disease
    • Almost identical to respiratory bronchiolitis on histology
  • Usual interstitial pneumonia
    • Marked dense fibrosis, architectural distortion and fibroblastic focus are seen
    • Clinically, UIP / IPF is more progressive and not responding to corticosteroid therapy
Board review style question #1
    Which clinical and morphological finding is NOT suggestive for DIP?

  1. A history of passive smoking
  2. Bilateral ground glass opacity
  3. Intra-alveolar cells positive for M. tuberculosis
  4. Intra-alveolar cells positive for Prussian blue
  5. Intra-alveolar giant cells
Board review style answer #1
C. Accumulated intra-alveolar cells of DIP are called smoker’s macrophages, which harbor aspirated particles in the cytoplasm. DIP is not related to mycobacterial infection.

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Reference: Desquamative interstitial pneumonitis
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