Diffuse lung diseases

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Diffuse lung diseases, abbreviated DLD, are a group of uncommon pathologies, also known as idiopathic interstitial pneumonias, abbreviated IIPs, and interstitial lung disease.

They are a subgroup of the medical lung diseases.

Diffuse lung disease is the preferred term, as some diseases lumped into this group have involvement of the alveoli, i.e. are not interstitial. Also, some DLDs are not considered idiopathic, e.g. LIP is caused by smoking.

An introduction to pulmonary pathology is found in the pulmonary pathology article.

Overview - histologic classification

Idiopathic interstitial pneumonia can be subclassified based on histologic appearance into the following patterns:[4][5]

Histology Clinical Correlates Associations
Desquamative interstitial pneumonia (DIP) DIP Smoking
Diffuse alveolar damage (DAD) ARDS, AIP, TRALI ARDS: trauma, infection; TRALI: blood transfusion; AIP: viral (???)
Nonspecific interstitial pneumonia (NSIP) NSIP ???
Respiratory bronchiolitis RB-ILD Smoking
Usual interstitial pneumonia (UIP) CVD, IPF, drug toxicity, pneumoconiosis Allergen (hypersensitivity pneumonitis), idiopathic, autoimmune
Organizing pneumonia Cryptogenic organizing pneumonia autoimmune (???)
Lymphoid interstitial pneumonia (LIP) LIP Viral/autoimmune

ARDS = adult respiratory distress syndrome, AIP = acute interstitial pneumonia, TRALI = transfusion related acute lung injury, CVD = collagen vascular disease, IPF = idiopathic pulmonary fibrosis.


Notes:

  • Usual interstitial pneumonia is the most common type of ILD.[6]

Specific diseases/pattterns

Diffuse alveolar damage

  • Abbreviated DAD.

General

DAD is the histologic correlate of:

  • Adult respiratory distress syndrome (ARDS).
  • Acute interstitial pneumonia (AIP).
  • Transfusion related acute lung injury (TRALI).

Microscopic

Features:[7]

  • Early:
    • Hyaline membrane: debris (pink crap) lines the alveolar spaces.
  • Intermediate:
    • Macrophage proliferation.
  • Late:
    • Interstitial inflammation.
    • Fibrosis.

Images:

Usual interstitial pneumonia

  • Abbreviated UIP.

General

  • It is sometimes used incorrectly as a synoym for idiopathic pulmonary fibrosis.
  • Cannot be diagnosed via bronchoscopic or transbronchial biopsy.[8]

Epidemiology

  • Disease of the old - rare in under 50 years old.[9]
  • Dismal prognosis - mean survival after diagnosis ~ 2.8 years.[10]

Differential diagnosis

UIP is seen in:[11]

Radiology

  • Honeycombing - multiple defects that obliterate the normal lung architecture - multiple spherical voids in the lung parenchyma; radiologically these are seen as lucencies.[14]
    • Usually subplural, i.e. peripheral lung.
    • Classically lower lobe predominant.
    • Associated with interstitial thickening. (???)

Note:

  • Cysts - have thin walls (think of emphysema, lymphangioleiomyomatosis et cetera).
    • Cysts may be isolated/not close to a neighbour.
    • Medcyclopaedia defines it as: thin-walled, well-demarcated and >1 cm.[15]

Microscopic

Features:[16]

  • Fibroblast foci:
    • "Crescent-shaped bulge" of fibroblasts -- a rounded projection of spindle cells into the airspace.
    • Location: in the areas of transisition between active inflammation and old inflammation.[17]
    • Note: Technically, fibroblast foci are composed of myofibroblasts.[18]
  • Interstitial inflammation,
  • Microscopic honeycombing,
    • Typically peripheral - cysts lined by ciliated epithelium.
  • Spatial heterogeneity - patchy lesional distribution (areas of abnormal and normal lung may appear beside one another).
  • Temporal heterogeneity - lesions of differing age side-by-side.[19]

Notes:

  • Disease worse distant from large airways: lower lung field predominance, typically worse at periphery of lobule and lung.[20]
  • Heterogeneity of inflammation: airspace macrophages & inflammation minimal in honeycombed foci.

Asbestosis

General

  • Important to diagnose... asbestosis = compensation.

Microscopic

  • Histologic appearance as for UIP -- plus ferruginous bodies.
    • Segmented twirling batton with long slender fibre within.

Image(s):

Non-specific interstitial pneumonia

  • Abbreviated NSIP.
  • Better prognosis than UIP.
  • Some radiologists and pathologists don't believe in this entity.

Gross/Radiology

  • No honeycombing.
  • Fibrosis usually lower lung zone.
  • Patchy ground glass.

Microscopic

  • Fibrosis:
    • May be uniform.
    • "Linear fibrosis" has a good prognosis - should be mentioned in the report.
      • Linear fibrosis = fibrosis that follows alveolar walls + no architectural distortion.
  • +/-Lymphoid nodules - assoc. with collagen vascular disease.

Notes:

  • Like UIP... also temporally and spatially heterogeneous.
  • Inflammation in NSIP usually more prominent than in UIP.
  • No honeycombing - key difference between UIP and NSIP.

DDx

  • Collagen vascular disease.
  • Drug reaction.
  • Hypersensitivity pneumonitis (extrinic allergic alveolitis).

Hypersensitivity pneumonitis

  • AKA extrinsic allergic alveolitis
  • Exposure to stuffs... e.g. moldy hay - Farmer's lung, atypical mycobacteria - hot tub lung.
  • Upper lung predominant disease (???).

Microscopic

Features:

  • Lesions have centrilobular prominence - important feature. [21]
    • Allergens enter lung through airway which has a centrilobular location.
  • Granulomata (not typically seen in UIP) - important feature.[21]
  • Chronic interstitial inflammation consisting primarily of lymphocytes.
  • Interstitial fibrosis.
  • Air space involvement (alveolitis).

Images:


See also

References

  1. ↑ Nicholson AG (November 2002). "Classification of idiopathic interstitial pneumonias: making sense of the alphabet soup". Histopathology 41 (5): 381-91. PMID 12405906. http://www3.interscience.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0309-0167&date=2002&volume=41&issue=5&spage=381.
  2. ↑ Flaherty KR, King TE, Raghu G, et al (October 2004). "Idiopathic interstitial pneumonia: what is the effect of a multidisciplinary approach to diagnosis?". Am. J. Respir. Crit. Care Med. 170 (8): 904-10. doi:10.1164/rccm.200402-147OC. PMID 15256390. http://ajrccm.atsjournals.org/cgi/pmidlookup?view=long&pmid=15256390.
  3. ↑ Kim DS, Collard HR, King TE (June 2006). "Classification and natural history of the idiopathic interstitial pneumonias". Proc Am Thorac Soc 3 (4): 285-92. doi:10.1513/pats.200601-005TK. PMID 16738191. http://pats.atsjournals.org/cgi/pmidlookup?view=long&pmid=16738191.
  4. ↑ Leslie KO, Wick MR. Practical Pulmonary Pathology: A Diagnostic Approach. Elsevier Inc. 2005. ISBN 978-0-443-06631-3.
  5. ↑ "American Thoracic Society/European Respiratory Society International Multidisciplinary Consensus Classification of the Idiopathic Interstitial Pneumonias. This joint statement of the American Thoracic Society (ATS), and the European Respiratory Society (ERS) was adopted by the ATS board of directors, June 2001 and by the ERS Executive Committee, June 2001". Am. J. Respir. Crit. Care Med. 165 (2): 277-304. January 2002. PMID 11790668. http://ajrccm.atsjournals.org/cgi/pmidlookup?view=long&pmid=11790668.
  6. ↑ Visscher DW, Myers JL (June 2006). "Histologic spectrum of idiopathic interstitial pneumonias". Proc Am Thorac Soc 3 (4): 322-9. doi:10.1513/pats.200602-019TK. PMID 16738196. http://pats.atsjournals.org/cgi/pmidlookup?view=long&pmid=16738196.
  7. ↑ Klatt, Edward C. (2006). Robbins and Cotran Atlas of Pathology (1st ed.). Saunders. pp. 103. ISBN 978-1416002741.
  8. ↑ Leslie, Kevin O.; Wick, Mark R. (2004). Practical Pulmonary Pathology: A Diagnostic Approach (1st ed.). Churchill Livingstone. pp. 186. ISBN 978-0443066313.
  9. ↑ AC UBC S.102.
  10. ↑ Bjoraker, JA.; Ryu, JH.; Edwin, MK.; Myers, JL.; Tazelaar, HD.; Schroeder, DR.; Offord, KP. (Jan 1998). "Prognostic significance of histopathologic subsets in idiopathic pulmonary fibrosis.". Am J Respir Crit Care Med 157 (1): 199-203. PMID 9445300.
  11. ↑ Wick, Mark R.; Leslie, Kevin (2005). Practical pulmonary pathology: a diagnostic approach. Edinburgh: Churchill Livingstone. ISBN 0-443-06631-0. OCLC 156861539.
  12. ↑ Mitchell, Richard; Kumar, Vinay; Fausto, Nelson; Abbas, Abul K.; Aster, Jon (2011). Pocket Companion to Robbins & Cotran Pathologic Basis of Disease (8th ed.). Elsevier Saunders. pp. 374. ISBN 978-1416054542.
  13. ↑ Rossi SE, Erasmus JJ, McAdams HP, Sporn TA, Goodman PC (2000). "Pulmonary drug toxicity: radiologic and pathologic manifestations". Radiographics : a review publication of the Radiological Society of North America, Inc 20 (5): 1245-59. PMID 10992015.
  14. ↑ http://www.medcyclopaedia.com/library/topics/volume_v_1/h/honeycombing.aspx
  15. ↑ http://www.medcyclopaedia.com/library/topics/volume_v_1/l/lung_cyst.aspx
  16. ↑ Leslie, Kevin O.; Wick, Mark R. (2004). Practical Pulmonary Pathology: A Diagnostic Approach (1st ed.). Churchill Livingstone. pp. 186-9. ISBN 978-0443066313.
  17. ↑ http://www.epler.com/IPFWhat%27sIPFDiseaseInformation2.htm
  18. ↑ Leslie, Kevin O.; Wick, Mark R. (2004). Practical Pulmonary Pathology: A Diagnostic Approach (1st ed.). Churchill Livingstone. pp. 189. ISBN 978-0443066313.
  19. ↑ H. 8 July, 2009.
  20. ↑ A. Churg. UBC S.103.
  21. ↑ 21.0 21.1 PMID 16061708.
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