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Diffuse Parenchymal Lung Disease Diffuse Parenchymal Lung Diseases With an Unknown Cause ldiopathic Pulmonary Fibrosis Idiopathic pulmonary fibrosis (lPF), r,r,hich is associ:rted with the histopathologic pattern ol UIP. is the most common idiopathic form of DPLD. Deemed to be a reflection of d1,s regulated flbrosis in response to alveolar epithelial injury. it typically presents with chronic cough and dyspnea in patients belween 50 and 70 years of age. Lung examination is notable fbr bibasil:rr Velcro like inspiratory crackles. Clubbing is pre sent in up to 50',{, of patients. Sn.roking is considered a risk firctor, and patients are of ten treated fbr COPD without signili cant improvement. Chest radiographs may demonstrate bibasilar reticular changes. Characteristic HRCT abnormalities \ include bilateral. subpleural, and basal predominant reticular Fl G U R E 7. Chest CT scan demonstrating nonspecific interstitial pneumonia with scattered bilateral ground'glass opacities (b/ue arrow)and areas of subpleural changes. Advanced cases may develop traction bronchiectasis sparing(red arrow) in the lower lung section. Also noted incidentally is trace pneumo' with subpleural clusters of palisading cysts called honeycomb mediastinum (yel/ow arrow)onlhe right lung. ing (Figure 6). When HRCT findings are classic lbr UIP, lung biopsy is not necessary lbr diagnosis. IPF is progressive, with a median survival of 3 tci 5 years atter progression, they are not curative. Referral to a pulmonologist diagnosis. Patients may experience acute exacerbations with a or ILD center is appropriate before initiating treatment $'ith r:rpid worsening o1' symptoms and development of bilateral these medications. ground glass opacities superimposed on areas of background Given the progressive and unpredictable clinical course fibrosis. These events may represent an acceleration of the dis of IPF. early referral to a lung transplant center is strong\' ease. Even though glucocorticoids and antibiotics are fiequently recommended. used, there are no proven therapies lbr acute exacerbations ot'lPF, Palliative care consultation to establish advanced care Management of patients rt,itl.r IPF should include consid plans should be considered for patients n,ith IPF r,r'ho are not eration of antifibrotic therapies and oxygen supplementation candidates for lung transplantation. fbr hypoxemia. In 201,1 the FDA approved nintedanib. a tyros XEY POITIS ine kinase inhibitor, and pirfenidone. an antifibrotic agent, o When high resolution CT findings are classic tbr usual HVC fbr use in patients with IPF. Although the mechanisms of these lvvo medications differ, the clinical response is quite interstitial pneumonia. lung biopsy is not necessary for diagnosis. similar, with both demonstrating a decline in the rate of pro- gression of disease. Although these medications delay IPF . Therapy with nintedanib and pirf'enidone decreases the rate of progression of idiopathic pulmonary fibrosis but is not curative.

Diffuse Parenchymal Lung Diseases With an Unknown Cause ldiopathic Pulmonary Fibrosis Idiopathic pulmonary fibrosis (lPF), r,r,hich is associ:rted with the histopathologic pattern ol UIP. is the most common idiopathic form of DPLD. Deemed to be a reflection of d1,s regulated flbrosis in response to alveolar epithelial injury. it typically presents with chronic cough and dyspnea in patients belween 50 and 70 years of age. Lung examination is notable fbr bibasil:rr Velcro like inspiratory crackles. Clubbing is pre sent in up to 50',{, of patients. Sn.roking is considered a risk firctor, and patients are of ten treated fbr COPD without signili cant improvement. Chest radiographs may demonstrate bibasilar reticular changes. Characteristic HRCT abnormalities \ include bilateral. subpleural, and basal predominant reticular Fl G U R E 7. Chest CT scan demonstrating nonspecific interstitial pneumonia with scattered bilateral ground'glass opacities (b/ue arrow)and areas of subpleural changes. Advanced cases may develop traction bronchiectasis sparing(red arrow) in the lower lung section. Also noted incidentally is trace pneumo' with subpleural clusters of palisading cysts called honeycomb mediastinum (yel/ow arrow)onlhe right lung. ing (Figure 6). When HRCT findings are classic lbr UIP, lung biopsy is not necessary lbr diagnosis. IPF is progressive, with a median survival of 3 tci 5 years atter progression, they are not curative. Referral to a pulmonologist diagnosis. Patients may experience acute exacerbations with a or ILD center is appropriate before initiating treatment $'ith r:rpid worsening o1' symptoms and development of bilateral these medications. ground glass opacities superimposed on areas of background Given the progressive and unpredictable clinical course fibrosis. These events may represent an acceleration of the dis of IPF. early referral to a lung transplant center is strong\' ease. Even though glucocorticoids and antibiotics are fiequently recommended. used, there are no proven therapies lbr acute exacerbations ot'lPF, Palliative care consultation to establish advanced care Management of patients rt,itl.r IPF should include consid plans should be considered for patients n,ith IPF r,r'ho are not eration of antifibrotic therapies and oxygen supplementation candidates for lung transplantation. fbr hypoxemia. In 201,1 the FDA approved nintedanib. a tyros XEY POITIS ine kinase inhibitor, and pirfenidone. an antifibrotic agent, o When high resolution CT findings are classic tbr usual HVC fbr use in patients with IPF. Although the mechanisms of these lvvo medications differ, the clinical response is quite interstitial pneumonia. lung biopsy is not necessary for diagnosis. similar, with both demonstrating a decline in the rate of pro- gression of disease. Although these medications delay IPF . Therapy with nintedanib and pirf'enidone decreases the rate of progression of idiopathic pulmonary fibrosis but is not curative. Nonspecific lnterstitial Pneumonia Although nonspecific interstitial pneumcrnia (NSIP) is a corn mon variant in CTD associated DPLD. idiopathic NSIP is a distinct clinical entity. Differentiation of idiopathic NSIP fiom IPF is critical as the tlvo diseases have distinct treatment algo- rithms and IPF has a worse prognosis. NSIP gpically affects a younger population than tPF. The HRCT scan typically dem<-rn strates bilateral lower-lobe reticular changes and scattered ground glass opacities (Figure 7). Although NSIP can progress to fibrosis. honeycombing, which is a classic feature for UIP. is rarely seen in NS[P. Biopsy is lrequently warranted to confirm the diagnosis ancl exclude alternate pathologies and may reveal inflammation and fibrosis. On the basis of'the extent of inflam mation and fibrosis. cellular and fibrotic fbrrns of NSIP are t I G U R E 6. High-resolution chest CT scan demonstrating the typical findings in idiopathic pulmonary fibrosis, including increased reticular changes that are described. The cellular fbrm has a better prognosis and fy-pi predominantly peripheral and basilar in distribution, honeycombing (at the left cally responds to immunosuppressive treatments. Although base), and absence of significant ground-glass opacification. the overall prognosis is better than for IPF, the 5 year mortality

Nonspecific lnterstitial Pneumonia Although nonspecific interstitial pneumcrnia (NSIP) is a corn mon variant in CTD associated DPLD. idiopathic NSIP is a distinct clinical entity. Differentiation of idiopathic NSIP fiom IPF is critical as the tlvo diseases have distinct treatment algo- rithms and IPF has a worse prognosis. NSIP gpically affects a younger population than tPF. The HRCT scan typically dem<-rn strates bilateral lower-lobe reticular changes and scattered ground glass opacities (Figure 7). Although NSIP can progress to fibrosis. honeycombing, which is a classic feature for UIP. is rarely seen in NS[P. Biopsy is lrequently warranted to confirm the diagnosis ancl exclude alternate pathologies and may reveal inflammation and fibrosis. On the basis of'the extent of inflam mation and fibrosis. cellular and fibrotic fbrrns of NSIP are t I G U R E 6. High-resolution chest CT scan demonstrating the typical findings in idiopathic pulmonary fibrosis, including increased reticular changes that are described. The cellular fbrm has a better prognosis and fy-pi predominantly peripheral and basilar in distribution, honeycombing (at the left cally responds to immunosuppressive treatments. Although base), and absence of significant ground-glass opacification. the overall prognosis is better than for IPF, the 5 year mortality 30

Diffuse Parenchymal Lung Disease of idiopathic NSIP remains approximately 15')1, to 25')(,. As with f,EY POIlIT' lPF. selected patients may benefit Irom lung transplantation. . Cryptogenic organizing pneumonia typically presents IEV PomT as cough, fever, and malaise lasting weeks to months, . On high-resolution CT, nonspecific interstitial pneumo- and imaging findings mimic infectious pneumonia; nia typically demonstrates bilateral lower-lobe reticular treatment is with glucocorticoids. changes and areas of ground-glass opacification. . The diagnosis of cryptogenic organizing pneumonia HVC (COP) may not require lung biopsy if the clinical pres-

of idiopathic NSIP remains approximately 15')1, to 25')(,. As with f,EY POIlIT' lPF. selected patients may benefit Irom lung transplantation. . Cryptogenic organizing pneumonia typically presents IEV PomT as cough, fever, and malaise lasting weeks to months, . On high-resolution CT, nonspecific interstitial pneumo- and imaging findings mimic infectious pneumonia; nia typically demonstrates bilateral lower-lobe reticular treatment is with glucocorticoids. changes and areas of ground-glass opacification. . The diagnosis of cryptogenic organizing pneumonia HVC (COP) may not require lung biopsy if the clinical pres- Cryptogenic Organizing Pneumonia entation and high resolution CT findings are consistent Organizing pneumonia is defined by histopathologic findings with COP; for cases with atypical presentation, lung of patchy proliferation of granulation tissue that affects the biopsy helps make the diagnosis. terminal bronchioles and alveolar ducts and spaces and is associated with surrounding inflammation. This pattern is Acute lnterstitial Pneumonia nonspecitic and often fbllows or is associated with various Acute interstitial pneumonia develops rapidly over days to types of injury to the lung. including acute infection, radiation weeks, resulting in acute respiratory fhilure with bilateral exposure, drug-induced pneumonitis, and autoimmune dis alveolar opacities or.r HRCT of the cl.rest. The pathologic eases. In patients in whom no cause is identified, the diagnosis findings on open lung biopsy are those of diffuse alveolar is termed cryptogenic organizing pneumonia (COP). damage. This process is clinically, radiographically, and path Patients lvith COP typically have a subacute presentation ologically indistinguishable fiom acute respiratory distress with cough, iever, and malaise over weeks to montl.rs. lnitial syndrome (ARDS). The absence of known risk factors for the chest radiographs typically demonstrate patchy opacities that development of ARDS suggests a diagnosis of acute intersti mimic pneumonia, and as a result, patients are often initially tial pneumonia. misdiagnosed with pneumonia and treated with antibiotics Management includes ventilatory support and critical (Figure 8). However, nonresolving symptonls and failure to care, as it does for patients with ARDS. Mortality renrains high respond to antibiotics should raise suspicion for orgarrizing (approximately 50'1,), and tl.rose who recover from the initial pneumonia or COP HRCT findings can range from ground illness often have complications. are at risk for the develop glass opacities to areas of alveolar consolidation resembling an ment of chronic lung disease, and may have a relapsc. Patier-rts infectious pneumonia. The diagnosis may not require lung are often treated with high dose giucocorticoids, although biopsy if the clinical presentation and HRCT findings are con strong evidence to support their use is lacking. sistent with COP. For cases with atypical presentation, lung biopsy helps make the dicgnosis. rtv P0t ltT o Acute interstitial pneumonia is clinically, radiographically, Patients with COP respond well to glucocorticoid therapy. Relapses of COP with tapering of glucocorticoids are common. and pathologically indistinguishable from acute respira ln such settings, consideration of glucocorticoid-sparing ther tory distress syndrome (ARDS), but patients lack risk apies is warranted. factors for ARDS.

Cryptogenic Organizing Pneumonia entation and high resolution CT findings are consistent Organizing pneumonia is defined by histopathologic findings with COP; for cases with atypical presentation, lung of patchy proliferation of granulation tissue that affects the biopsy helps make the diagnosis. terminal bronchioles and alveolar ducts and spaces and is associated with surrounding inflammation. This pattern is Acute lnterstitial Pneumonia nonspecitic and often fbllows or is associated with various Acute interstitial pneumonia develops rapidly over days to types of injury to the lung. including acute infection, radiation weeks, resulting in acute respiratory fhilure with bilateral exposure, drug-induced pneumonitis, and autoimmune dis alveolar opacities or.r HRCT of the cl.rest. The pathologic eases. In patients in whom no cause is identified, the diagnosis findings on open lung biopsy are those of diffuse alveolar is termed cryptogenic organizing pneumonia (COP). damage. This process is clinically, radiographically, and path Patients lvith COP typically have a subacute presentation ologically indistinguishable fiom acute respiratory distress with cough, iever, and malaise over weeks to montl.rs. lnitial syndrome (ARDS). The absence of known risk factors for the chest radiographs typically demonstrate patchy opacities that development of ARDS suggests a diagnosis of acute intersti mimic pneumonia, and as a result, patients are often initially tial pneumonia. misdiagnosed with pneumonia and treated with antibiotics Management includes ventilatory support and critical (Figure 8). However, nonresolving symptonls and failure to care, as it does for patients with ARDS. Mortality renrains high respond to antibiotics should raise suspicion for orgarrizing (approximately 50'1,), and tl.rose who recover from the initial pneumonia or COP HRCT findings can range from ground illness often have complications. are at risk for the develop glass opacities to areas of alveolar consolidation resembling an ment of chronic lung disease, and may have a relapsc. Patier-rts infectious pneumonia. The diagnosis may not require lung are often treated with high dose giucocorticoids, although biopsy if the clinical presentation and HRCT findings are con strong evidence to support their use is lacking. sistent with COP. For cases with atypical presentation, lung biopsy helps make the dicgnosis. rtv P0t ltT o Acute interstitial pneumonia is clinically, radiographically, Patients with COP respond well to glucocorticoid therapy. Relapses of COP with tapering of glucocorticoids are common. and pathologically indistinguishable from acute respira ln such settings, consideration of glucocorticoid-sparing ther tory distress syndrome (ARDS), but patients lack risk apies is warranted. factors for ARDS. Combined Pulmonary Fibrosis and Emphysema Combined pulmonary {ibrosis and emphysema (CPFE) is a distinct clinical entity wherein fibrotic lung disease, similar to lPF, coexists with emphysematous changes in the sanre patier.rt (Figure 9). Even with advanced architectural changes, lung function studies miry reveal presenred spirometry and lung volumes. Marked impairment in gas exchange manifesting as reduced diffusing capacity is typical tbr CPFE. I'resence of pulmonary hypertension in patients with CPFE portends a poor prognosis. Lung transplant is the only curative therapy.

Combined Pulmonary Fibrosis and Emphysema Combined pulmonary {ibrosis and emphysema (CPFE) is a distinct clinical entity wherein fibrotic lung disease, similar to lPF, coexists with emphysematous changes in the sanre patier.rt (Figure 9). Even with advanced architectural changes, lung function studies miry reveal presenred spirometry and lung volumes. Marked impairment in gas exchange manifesting as reduced diffusing capacity is typical tbr CPFE. I'resence of pulmonary hypertension in patients with CPFE portends a poor prognosis. Lung transplant is the only curative therapy. Sarcoidosis Sarcoidosis is a granulomatous disease of unknown cause that

Combined Pulmonary Fibrosis and Emphysema Combined pulmonary {ibrosis and emphysema (CPFE) is a distinct clinical entity wherein fibrotic lung disease, similar to lPF, coexists with emphysematous changes in the sanre patier.rt (Figure 9). Even with advanced architectural changes, lung function studies miry reveal presenred spirometry and lung volumes. Marked impairment in gas exchange manifesting as reduced diffusing capacity is typical tbr CPFE. I'resence of pulmonary hypertension in patients with CPFE portends a poor prognosis. Lung transplant is the only curative therapy. Sarcoidosis Sarcoidosis is a granulomatous disease of unknown cause that F lGU R E J 8. Chest CIscan demonstrating bilateral patchy opacities with air can alfect any organ system. More than 90',1, of patients with sarcoidosis have lung involvement. The prevalence of s:rrcoido sis is approximately 10 to 20 per 100,000 irrdividuals. Sarcoidosis affects Black persons more frequently than bronchograms mimicking pneumonia.Transbronchial biopsies lrom right middle lobe revealed organizing pneumonia and 0pacities resolved with oral glucocorticoids. White persons and typically occurs in younger patients. Many

F lGU R E J 8. Chest CIscan demonstrating bilateral patchy opacities with air can alfect any organ system. More than 90',1, of patients with sarcoidosis have lung involvement. The prevalence of s:rrcoido sis is approximately 10 to 20 per 100,000 irrdividuals. Sarcoidosis affects Black persons more frequently than bronchograms mimicking pneumonia.Transbronchial biopsies lrom right middle lobe revealed organizing pneumonia and 0pacities resolved with oral glucocorticoids. White persons and typically occurs in younger patients. Many 31