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GLOSSARY & ABBREVIATIONS

acute interstitial pneumonia
(AIP, also known as Hamman-Rich syndrome)

AIP is an acute, idiopathic, and rapidly progressive disease of the lung often leading to fulminant respiratory failure and acute respiratory distress syndrome.¹ It can be distinguished clinically from other types of interstitial pneumonia by the rapid onset of respiratory failure in a patient without preexisting lung disease.² AIP is classified by the American Thoracic Society and European Respiratory Society under major idiopathic interstitial pneumonia and compared to other rare or unclassifiable idiopathic interstitial pneumonia.¹

Mrad A, Huda N. Acute interstitial pneumonia. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022. PMID: 32119316.

cryptogenic organizing pneumonia (COP)

Organizing pneumonia (OP) is a type of inflammatory reaction of the lung resulting in a pathological syndrome displaying a pattern of intra-alveolar buds of granulation consisting of fibroblasts and myofibroblasts mixed with loose connective matrix. If OP is the result of an underlying disorder (eg, infection, drug toxicity, or connective tissue disease), it is termed secondary OP. When no cause is established, it is termed cryptogenic organizing pneumonia (COP).³

Cottin V, Cordier JF. Cryptogenic organizing pneumonia. Semin Respir Crit Care Med. 2012;33:462-475. doi: http://dx.doi.org/10.1055/s-0032-1325157.

desquamative interstitial pneumonia (DIP)

DIP is a rare type of idiopathic interstitial pneumonia, characterized by large numbers of macrophages in the alveolar spaces and associated with interstitial inflammation and/or fibrosis.^4,5 Lymphoid nodules are common along with a sparse but distinct eosinophil infiltrate.⁵ Most cases of DIP are caused by cigarette smoking, but drugs and other inhaled agents, including marijuana smoke, can also produce the same disease.^4,5

Tazelaar HD, Wright JL, Churg A. Desquamative interstitial pneumonia. Histopathology. 2011;58(4):509-16. doi: 10.1111/j.1365-2559.2010.03649.x. Epub 2010 Sep 21. PMID: 20854463.

hypersensitivity pneumonitis (HP, also known as extrinsic allergic alveolitis)

HP is a complex pulmonary syndrome mediated by the immune system and caused by inhalation of a wide variety of antigens in patients previously sensitized.⁶ The pathobiology of the disease is not fully understood, but in addition to the triggers that initiate the disease, host/genetic factors are thought to be important, as only a minority of exposed individuals develop HP. Acute forms generally resolve without sequelae, while chronic forms, which are caused by persistent low-grade exposures, are associated with poor prognosis.⁷

Spagnolo P, Rossi G, Cavazza A, et al. Hypersensitivity pneumonitis: a comprehensive review. J Investig Allergol Clin Immunol. 2015;25(4):237-50. PMID: 26310038.

idiopathic non-specific interstitial pneumonia (iNSIP)

NSIP suggested by HRCT or identified on lung pathology is often the result of connective tissue disease, drug toxicity, HP or other causes, but when a cause cannot be attributed to the NSIP pattern it may be classified as iNSIP. Patients with iNSIP typically present in mid-adulthood with dyspnea, cough, and often fever and fatigue. The disease has a female predominance, and is more frequently diagnosed in never-smoker patients. It is highly important to complete a thorough history and assessment for other causes to rule out idiopathic NSIP.⁸ Multidisciplinary discussion (MDD) is especially important to establish the diagnosis of iNSIP.⁸

Belloli EA, Beckford R, Hadley R, Flaherty KR. Idiopathic non-specific interstitial pneumonia. Respirology. 2016;21(2):259-68. doi: 10.1111/resp.12674. Epub 2015 Nov 13. PMID: 26564810.

idiopathic pulmonary fibrosis (IPF)

IPF is a progressive and fatal lung disease with increasing prevalence and a median survival of 3–5 years after diagnosis. IPF is characterized by altered cellular composition and dysfunction of resident and immune cells in the lung, leading to an excess of extracellular matrix formation and progressive fibrosis.⁹

Podolanczuk AJ, Wong AW, Saito S, Lasky JA, Ryerson CJ, Eickelberg O. Update in interstitial lung disease 2020. Am J Respir Crit Care Med. 2021;203(11):1343-1352. doi: 10.1164/rccm.202103-0559UP. PMID: 33835899; PMCID: PMC8759209.

interstitial lung disease (ILD)

ILDs are a heterogeneous group of more than 200 conditions characterized by varying degrees of fibrotic or inflammatory abnormalities of the lung, or a combination of the two.¹⁰ ILDs are caused by both known and unknown factors. ILDs can be acute or chronic and may be self-limiting or progressive.¹⁰

Yioe V, Phillips G, Spencer LG. Interstitial lung disease on the acute take for the non-respiratory physician. Clin Med (Lond). 2021;21(6):e584-e590. doi: 10.7861/clinmed.2021-0694. PMID: 34862217; PMCID: PMC8806283.

lymphangioleiomyomatosis (LAM)

LAM is a rare disease almost exclusively affecting women of childbearing age.^11,12 LAM is a systemic disease with the primary manifestations being pulmonary. It is characterized by the presence of abnormal smooth muscle cells (LAM cells) that infiltrate the lungs and airways, leading to lung cysts and pneumothoraces.¹²

Cohen MM, Pollock-BarZiv S, Johnson SR. Emerging clinical picture of lymphangioleiomyomatosis. Thorax. 2005;60(10):875-9. doi: 10.1136/thx.2004.035154. Epub 2005 Jul 29. PMID: 16055626; PMCID: PMC1747203.

lymphoid interstitial pneumonia (LIP, also known as lymphocytic interstitial pneumonia)

LIP is a rare interstitial lung disease frequently associated with connective tissue diseases or infections.¹³ LIP presents with cough, progressive dyspnea, and crackles.^14,15 Idiopathic LIP is rare, so every attempt must be made to diagnose underlying conditions when LIP is diagnosed.¹⁵ Demonstrating polyclonality with immunohistochemistry is the key to differentiating LIP from lymphoma.¹³ The 5-year mortality remains as high as 50% and is likely to vary based on the underlying disease process.¹⁴

Panchabhai TS, Farver C, Highland KB. Lymphocytic interstitial pneumonia. Clin Chest Med. 2016;37(3):463-74. doi: 10.1016/j.ccm.2016.04.009. Epub 2016 Jun 25. PMID: 27514593.

pleuroparenchymal fibroelastosis (PPFE)

PPFE is a rare idiopathic interstitial pneumonia with unique clinical, radiological, and pathological characteristics. PPFE presents with a combination of fibrosis involving the visceral pleura and fibroelastotic changes predominating in the subpleural lung parenchyma. While PPFE has been associated with a number of diseases, no single cause has been identified.¹⁶

Chua F, Desai SR, Nicholson AG, et al. Pleuroparenchymal fibroelastosis. A review of clinical, radiological, and pathological characteristics. Ann Am Thorac Soc. 2019;16(11):1351-1359. doi: 10.1513/AnnalsATS.201902-181CME. PMID: 31425665; PMCID: PMC6945468.

systemic sclerosis (SSc)

Systemic sclerosis (SSc) is a multisystem connective tissue disease characterized by fibrosis, and by vascular and immunological abnormalities. SSc is classified based on skin involvement and there are 2 main subtypes of SSc, limited cutaneous SSc (lcSSc) and diffuse cutaneous SSc (dcSSc). LcSSc is associated with skin thickening distal to the elbows, distal to the knees, and/or on the face without trunk involvement. DcSSc is associated with skin thickening proximal to the knees, on the face, and/or the trunk. Both subtypes can affect the lungs, as well as the gastrointestinal tract, kidneys, skeletal muscle, and pericardium.¹⁷

Adigun R, Goyal A, Hariz A. Systemic Sclerosis. 2022 May 8. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022. PMID:28613625.

ACE, angiotensin-converting enzyme
AIP, acute interstitial pneumonia
ANA, antinuclear antibody
ATA, anti-topoisomerase antibodies
BAL, bronchoalveolar lavage
CCP, cyclic citrullinated peptide
CHF, congestive heart failure
COP, cryptogenic organizing pneumonia
COPD, chronic obstructive pulmonary disease
CT, computed tomography
CTD, connective tissue disease
DIP, desquamative interstitial pneumonia
DL_CO, diffusing capacity of the lungs for carbon monoxide
dcSSc, diffuse cutaneous systemic sclerosis
FEV₁, forced expiratory volume in one second
FVC, forced vital capacity
GERD, gastroesophageal reflux disease
HLA, human leukocyte antigen
HP, hypersensitivity pneumonitis
HRCT, high-resolution computed tomography
HTN, hypertension
ILD, interstitial lung disease
iNSIP, idiopathic non-specific interstitial pneumonia
IPF, idiopathic pulmonary fibrosis
LAM, lymphangioleiomyomatosis
LIP, lymphoid interstitial pneumonia
MDD, multidisciplinary discussion
MI, myocardial infarction
NSIP, non-specific interstitial pneumonia
OP, organizing pneumonia
PFT, pulmonary function test
PPFE, pleuroparenchymal fibroelastosis
RA-ILD, rheumatoid arthritis-associated interstitial lung disease
RB-ILD, respiratory bronchiolitis-associated interstitial lung disease
RF, rheumatoid factor
RV, residual volume
Scl-70, scleroderma-70 (topoisomerase I)
SLB, surgical lung biopsy
SpO₂, oxygen saturation
SS-A, Sjögren’s syndrome-A (anti-Ro)
SS-B, Sjögren’s syndrome-B (anti-La)
SSc, systemic sclerosis
SSc-ILD, systemic sclerosis-associated interstitial lung disease
TBLC, transbronchial lung cryobiopsy
TLC, total lung capacity
TPO, thyroid peroxidase
uILD, unclassifiable interstitial lung disease
UIP, usual interstitial pneumonia
VATS, video-assisted thoracoscopic surgery

References:
1. Travis WD et al. Am J Respir Crit Care Med. 2013;188(6):733-748. 2. Bouros D et al. Eur Respir J. 2000;15:412-418. 3. Cottin V et al. Semin Respir Crit Care Med. 2012;33:462-475. 4. Godbert B et al. Eur Resp Rev. 2013;22(128):117-123. 5. Tazelaar HD et al. Histopathology. 2011;58(4):509-516. 6. Costabel U et al. Clin Chest Med. 2012;33(3):151-163. 7. Spagnolo P et al. J lnvestig Allergol Clin lmmunol. 2015;25(4):237-250. 8. Belloli EA et al. Respirology. 2016;21(2):259-268 9. Podolanczuk AJ et al. 2020. Am J Respir Crit Care Med. 2021;203(11):1343-1352. 10. Yioe V et al. Clin Med. 2021;21(6):e584-e590. 11. Cohen MM et al. Thorax. 2005;60(10):875-879. 12. Wakida K et al. Ann Thorac Surg. 2015;100:1105-1107. 13. Panchabhai T et al. Clin Chest Med. 2016;37(3):463-474. 14. Swigris J et al. Chest. 2002;122(6):2150-2164. 15. Cha S-I et al. Eur Respir J. 2006:28:364-369. 16. Chua F et al. Ann Am Thorac Soc. 2019;16(11):1351-1359. 17. Adigun R et al. Systemic Sclerosis. 2022 May 8. In: StatPearls [Internet]. 2022 Jan-. PMID: 28613625.

PATIENT CASE STUDY #2

67-year-old
male

Histopathology

Seven arrows pointing to fibroblast focus

Pathology
High magnification: Fibroblast focus (arrows)

Low magnification pathology image

Pathology
Low magnification:

honeycomb change
columnar respiratory epithelium outline of the cystic spaces
cystic spaces contain mucus and inflammatory cells

What are fibroblastic foci?

Fibroblastic foci are aggregates within the lung consisting of proliferating fibroblasts and myofibroblasts with a localized edge of spindle cells which indicate areas of active fibrosis.^1-3

Pathologist's note:

Additional sample shows patchy distribution of abnormalities.

References: 1. Visscher D, Myers J. Proc Am Thorac Soc. 2006;3(4):322-9. 2. du Bois RM. Chest. 2006;130(1):3-5. 3. Jones et al. JCI Insight. 2016;1(5):e86375.

Images used with permission from Visscher D, Myers J. Proc Am Thorac Soc. 2006;3(4):322-9.

Case study courtesy of and used with permission from Gregory Cosgrove, MD.