Bronchiolitis obliterans organizing pneumonia-like reactions: a nonspecific response or an atypical form of rejection or infection in lung allograft recipients?

[Cryptogenic organizing pneumonia]

INTRODUCTION

Organizing pneumonia is a particular type of inflammatory reaction of the lung which gives rise to a clinico-pathological syndrome. It is called "secondary" when a cause such as an infection, a drug toxicity, or a connective tissue disease can be identified, or "cryptogenic" when no cause is identified. The clinical picture is usually characterized by the subacute onset of fever, fatigue, cough and dyspnea, with multiple subpleural areas of consolidation on thoracic imaging.

STATE OF THE ART

Organizing pneumonia is characterised by the presence of buds of endoalveolar connective tissue. These result from an injury to the alveolar epithelium, followed by the deposition of fibrin in the alveolar spaces, and the migration of fibroblasts which produce a myxoid endoalveolar matrix. A remarkable feature of organizing pneumonia is the complete disappearance of these endoalveolar buds with corticosteroid treatment, in sharp contrast with what is seen in pulmonary fibrosis. The clinical response to corticosteroids is usually prompt and excellent. Relapses are frequent but usually benign.

PERSPECTIVES AND CONCLUSION

As the clinical, imaging and pathological characteristics of organizing pneumonia are now well established, many questions remain unanswered, such as the mechanisms involved in the complete reversibility of the pulmonary lesions, and the role of steroid-sparing treatments such as immunomodulatory macrolides.

Bronchiolitis obliterans organizing pneumonia: pathogenesis, clinical features, imaging and therapy review

Bronchiolitis obliterans organizing pneumonia (BOOP) was first described in the early 1980s as a clinicopathologic syndrome characterized symptomatically by subacute or chronic respiratory illness and histopathologically by the presence of granulation tissue in the bronchiolar lumen, alveolar ducts and some alveoli, associated with a variable degree of interstitial and airspace infiltration by mononuclear cells and foamy macrophages. Persons of all ages can be affected. Dry cough and shortness of breath of 2 weeks to 2 months in duration usually characterizes BOOP. Symptoms persist despite antibiotic therapy. On imaging, air space consolidation can be indistinguishable from chronic eosinophilic pneumonia (CEP), interstitial pneumonitis (acute, nonspecific and usual interstitial pneumonitis, neoplasm, inflammation and infection). The definitive diagnosis is achieved by tissue biopsy. Patients with BOOP respond favorably to treatment with steroids.

Pediatric lung transplantation: perspectives for the pathologist

Lung transplantation offers life-saving and life-extending treatment for children and adolescents with congenital and acquired forms of pulmonary and pulmonary vascular disease, for whom medical therapy is ineffective or insufficient for sustained response. This review summarizes the pathology related to lung transplantation for the practicing pediatric pathologist and also highlights aspects of lung transplantation unique to the pediatric population. Clinical issues related to availability of organs, candidate eligibility, surgical technique, and postoperative monitoring are discussed. Pathologic evaluation of routine surveillance transbronchial biopsies requires attention to acute cellular rejection, opportunistic infection, and other forms of acute and resolving lung injury. These findings are correlated in some cases with endobronchial biopsies and bronchoalveolar lavage as adjunctive tools in surveillance. Open or thoracoscopic biopsies also have diagnostic utility in cases with acute or chronic graft deterioration of uncertain etiology. Future challenges in pediatric lung transplantation are similar to those in the adult population, with continued efforts focused on prolonging graft survival, prevention of bronchiolitis obliterans syndrome due to chronic cellular rejection, and evaluation of humoral rejection.

Disease activity and 18F-FDG uptake in organising pneumonia: semi-quantitative evaluation using computed tomography and positron emission tomography

PURPOSE

The present study was conducted to evaluate whether( 18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) in combination with computed tomography (CT) reflects disease activity in patients with organising pneumonia.

METHODS

Eighty-eight subjects who were normal (n=66) or who had proven organising pneumonia (n=22) underwent FDG-PET and CT imaging. The subjects included 55 men and 33 women, ranging in age from 24 to 63 years (mean 47 years). PET and CT data sets were digitally fused using a conformational PET/CT fusion algorithm. All scans were evaluated independently by two chest radiologists who were unaware of other clinical data. The visual score, maximal and mean standardised uptake value (SUV), and maximal and mean lesion-to-normal tissue ratio (LNR) were calculated. The imaging results were compared with the laboratory and pulmonary function test results. The inflammatory cells in the lesions were quantified immunohistochemically.

RESULTS

The visual score, maximal and mean SUV, and maximal and mean LNR of the patients with organising pneumonia were significantly higher than those of the normal subjects. The patients with air-space consolidation had a significantly higher SUV than those without air-space consolidation (mean+/-SD 3.08+/-0.39 vs 2.35+/-0.56; p<0.05). The number of CD45(+) cells was positively correlated with the maximal SUV (r=0.632, p<0.01) and the maximal LNR (r=0.453, p<0.05). The number of CD8(+) T lymphocytes also showed positive correlations with the maximal SUV (r=0.540, p<0.01) and the maximal LNR (r=0.547, p<0.01).

CONCLUSION

Patients with organising pneumonia have an enhanced FDG accumulation which reflects the degree of disease activity.

The Organizing Pneumonias

In this comprehensive review, two very closely related interstitial pneumonias are discussed: the cryptogenic form of organizing pneumonia (COP); and secondary forms of organizing pneumonia (OP), which occur in association with identifiable medical conditions. Some newer and lesser known of these associated conditions are described, most importantly post-radiation OP.Rapidly progressive, corticosteroid-resistant and poor prognostic forms of OP have been described. These types purportedly occur more frequently in secondary OP. However, OPs frequently coexist with other interstitial pneumonias, especially when associated with connective tissue diseases. Therefore, tissue sampling error or an incorrect morphologic diagnosis can be the basis for the occurrence of clinically aggressive OPs. By using the 2002 American Thoracic Society/European Respiratory Society diagnostic criteria, some pre-2002 cases reported as OP would be re-classified today.Although COP is considered to have a good prognosis and to be corticosteroid responsive, approximately 70% of patients, treated with corticosteroids, relapse even during initial treatment. Multiple and late relapses occur in about one-third of the patients. We performed a meta-analysis of second-line treatment options for corticosteroid-refractory forms of OP. Three alternative nonsteroid agents - cyclophosphamide, azathioprine, and cyclosporin - have been used in combination with corticosteroids. On careful review, in a number of cases reported as secondary OP, other histologic interstitial patterns besides OP were described. The need for second-line therapy in these patients might have been dictated by the non-organizing pneumonic component. Most of the scant number of reports come from outside the US. World experience with these is limited, but good clinical outcomes have been noted, even in patients with interstitial patterns in addition to OP.The initiation of the OP tissue response in the bronchiolar and sub-bronchiolar location may be due to the presence of bronchiolar-associated lymphoid tissue found at the bifurcations of the bronchioles. Inhaled antigens stimulate granulocyte colony stimulating factor-mediated airway inflammation, followed later by CD44-mediated clearance. Repair requires intrabronchiolar formation of granulation tissue and a favorable ratio of matrix metalloproteinase to tissue inhibitors of metalloproteinase (MMP : TIMP) within the stroma. This reparative milieu allows extracellular matrix degradation and re-synthesis to occur. MMP-expressing fibroblasts then phagocytose the collagen fibrils and microfibrils produced earlier in repair, reversing the initial fibrosis.

The organizing pneumonias: an update and review

PURPOSE OF REVIEW

Basic information as well as more recent concepts regarding cryptogenic organizing pneumonia and secondary forms of the disease.

RECENT FINDINGS

More recently described and less well recognized illnesses associated with organizing pneumonia, such as organizing pneumonia associated with radiation, are enumerated. In vitro studies from separate laboratories are integrated to create a proposed model of the pathogenesis and repair mechanisms that occur in organizing pneumonias. Using current criteria, we note other interstitial lung processes, in addition to organizing pneumonia, are present in some earlier reports.

SUMMARY

Cryptogenic organizing pneumonia has been reported to respond to corticosteroids with clinico-radiographic resolution in 70-80% of cases. Treatment duration is lengthy, and despite this, recurrences and late recurrences are common. Rapidly progressive, steroid resistant and poor prognostic forms of organizing pneumonia have been described and have been reported more frequently with secondary organizing pneumonia. Since other histologic interstitial patterns often coexist with organizing pneumonia, tissue sampling error or an incorrect morphologic diagnosis can be the reason for aggressive clinical behavior. Steroid nonresponsive patients have been treated with secondary non-steroidal agents. Good clinical outcomes have been reported. Inhaled antigens stimulate GM-CSF-mediated airway inflammation in organizing pneumonia. Repair requires the following: granulation tissue, upon which re-epithelialization occurs; a favorable stromal ratio of matrix metalloproteinase to tissue inhibitors of metalloproteinase; concurrent resolution of inflammation; and stromal fibroblast ingestion of collagen produced earlier in repair, reversing the initial fibrosis.

Lung Transplantation Biopsy Specimens With Bronchiolitis Obliterans or Bronchiolitis Obliterans Organizing Pneumonia Due to Aspiration

Context.—Bronchiolitis obliterans (BO) is generally thought to be a marker of chronic airway rejection in patients who have undergone lung transplantation. Bronchoscopic biopsy specimens, by virtue of their small size, may sample only BO and not a lesion of bronchiolitis obliterans organizing pneumonia (BOOP). A role for ongoing chronic infection or aspiration has also been suggested, and the distinction of these etiologies may be difficult clinically and pathologically.

Objective.—To investigate the etiology of BO and BOOP in lung transplantation patients who had chronic aspiration.

Design.—This is a clinicopathologic study of 7 patients who had undergone lung transplantation in which biopsy findings suggested the possibility of chronic airway rejection but in which aspiration was subsequently proven as a cause of the bronchiolar disease.

Results.—All patients were men, who ranged in age from 19 to 57 years. A clinical diagnosis of aspiration was considered based on history, acid reflux testing, and radiographic findings in all 7 patients. Three patients had BO and 4 patients had BOOP. Histiocytic giant cells or foreign material was absent. The interval from transplantation to BO ascribed to aspiration ranged from 2.5 months to 7 years. The patients were treated aggressively with medication for gastroesophageal reflux disease. Their respiratory function and chest radiography results improved.

Conclusion.—Although BO may be a manifestation of rejection, it may also be a manifestation of aspiration. Because the latter is potentially correctable, aspiration should be considered etiologically in lung transplantation patients with either BO or BOOP. Reliable distinction between aspiration-related or rejection-related BO and BOOP cannot be made on morphologic grounds alone. Clinical and radiologic correlations are indicated to establish the distinction.

Bronchiolitis obliterans organizing pneumonia after orthotopic liver transplantation

Bronchiolitis obliterans organizing pneumonia (BOOP) has been described after bone marrow, lung, heart-lung, and renal transplantation, but rarely after orthotopic liver transplantation (OLT). We report a case of BOOP after OLT to emphasize BOOP as an under diagnosed and treatable cause of nonresolving pneumonia, which may not be preventable by maintenance low-dose prednisone. A 48-year-old man was hospitalized for dyspnea and cough one month after OLT. Among his medications were tacrolimus and prednisone. Physical examination was significant for lung crepitations and bilateral leg edema. Chest x-ray revealed bilateral infiltrates. Computed tomography (CT) of the chest demonstrated bilateral diffuse infiltrates with areas of sparing and nodularities. Bronchoscopy was normal and bronchoalveolar lavage was negative. Lung biopsy was performed and demonstrated serpiginous plugs of fibroblastic tissue filling the alveolar spaces, focal fibrosis of some alveolar septa, and reactive pneumocytic hyperplasia consistent with BOOP. Methylprednisolone was continued with clinical improvement and weaning from the ventilator, but subsequent sepsis and multisystem organ failure finally led to the patient's death.

A 59-year-old liver-transplanted woman with fever, dyspnea and pulmonary infiltrates

A 59-year-old woman was admitted to hospital 10 months after receiving a liver transplant (LT) for hepatitis C virus (HCV) cirrhosis because of fever, dyspnea and basal patchy peripheral infiltrates. Microscopic examinations and blood, sputum and BAL cultures were negative. Empirical anti-infective therapy was ineffective. Thoracoscopic lung biopsy was performed, and histology showed a pattern suggesting bronchiolitis obliterans organizing pneumonia (BOOP). Prednisone led to rapid clinical and radiologic improvement. BOOP has been anecdotally reported in LT cases, and this case was unrelated to any infectious agent. BOOP should be taken into account in the differential diagnosis of pneumonia in LT.

Bronchiolitis obliterans syndrome

BOS remains a difficult problem to control following lung transplantation, largely because of uncertainties regarding the underlying mechanisms that are responsible for it. Continued work on the pathogenesis of BOS is essential. The progressive nature and poor outlook when BOS stage 3 is reached indicates that current strategies should be focused on prevention and early intervention. There is a great need for randomized, controlled trials on intervention if the international transplant community is to make progress in this area.

Acute allograft rejection after lung transplantation: diagnosis and therapy

Acute rejection remains a significant problem after lung transplantation. While it generally is a treatable condition, significant resources and therapies are directed toward its prevention and resolution. Its larger significance undoubtedly rests in its contribution to the pathogenesis of BOS. Significant questions regarding the origins of AR, the role of LBB, alternative histologic appearances of acute allograft injury, and optimal therapy remain. Controversy regarding the utility of surveillance bronchoscopy and preemptive treatment of occult AR persists because of lack of conclusive evidence. Future investigations might resolve these matters and provide more efficacious and less toxic therapies that will hopefully reduce the impact of chronic rejection and improve long-term outcomes.

Bronchiolitis obliterans organizing pneumonia in an orthotopic liver transplant patient

A 67-year-old woman was hospitalized for progressive dyspnea on exertion. She had undergone orthotopic liver transplantation (OLT) 15 months before admission. Posttransplant therapy consisted of tacrolimus, trimethoprim/sulfamethoxazole, and prednisone (the latter two were discontinued after 1 year). Physical examination revealed fine bibasilar crackles. High-resolution chest CT demonstrated bilateral, diffuse, interstitial infiltrates. Symptoms persisted on i.v. antibiotics and bronchoscopy was performed demonstrating patchy fibroplastic plugs within air spaces consistent with bronchiolitis obliterans organizing pneumonia (BOOP). Prednisone was initiated and the patient had an uneventful recovery. BOOP was initially described as an idiopathic disease process with clinical, radiographic, pathological, and prognostic features distinguishing it from bronchiolitis obliterans and idiopathic pulmonary fibrosis. BOOP has been recognized as a complication of lung and bone marrow transplantation, but the mechanism is unknown. We report a case of BOOP after OLT to highlight the risk in all transplant patients as well as the protective effect of posttransplant prednisone.

Lung allograft dysfunction correlates with gamma-interferon gene expression in bronchoalveolar lavage

BACKGROUND

Preceding episodes of acute cellular rejection (ACR) may predispose lung allografts to the subsequent development of irreversible dysfunction or bronchiolitis obliterans syndrome (BOS). Other histologic patterns such as bronchiolitis obliterans with organizing pneumonia (BOOP), organizing pneumonia, lymphocytic bronchiolitis and diffuse alveolar damage (DAD) may also adversely affect allograft function. We have previously reported the predominant expression of Th1 cytokines (IL-2 and interferon gamma) in rejecting and Th2 (IL-10) in a tolerant model of rat lung transplantation. Here we correlate the "Th1/Th2 paradigm" in clinical lung transplantation with histologic findings and assess the effect on serial spirometric function.

METHODS

We examined the mRNA expression of IL-2, interferon gamma, IL-10 and ICAM-1 in 53 bronchoalveolar lavage (BAL) specimens from 23 lung transplant (LT) recipients utilizing qualitative "nested" reverse transcriptase polymerase chain reaction (RT-PCR). We also measured IgG1 and IgG2 levels in 44 BAL specimens by ELISA. The mRNA expression for cytokines, ICAM-1 and the IgG2/IgG1 ratios were correlated with the presence or absence of ACR and alternate "histologic patterns". Serial spirometry were analyzed for the 2-3 month interval before bronchoscopic (FOB) assessment to derive "baseline" forced expiratory volume-one second (FEV1) values. The change in FEV1 coincident with (deltaFEV1 pre) and for the 2-3 month interval subsequent to (deltaFEV1 post) FOB were expressed relative to "baseline" spirometric indexes.

RESULTS

Detection of mRNA for interferon gamma and ICAM-1 correlated significantly with ACR, whereas IL-2 and IL-10 expression did not correlate. IL-10 was virtually "ubiquitous" in most BAL samples irrespective of the presence or absence of ACR. The highest correlation was observed with interferon gamma for acute cellular rejection whereupon the sensitivity was 77.7%, specificity 87.7%, positive predictive value 73.6% and negative predictive value 88.2%, although for ICAM-1 these values were 75%, 65.7%, 50.0% and 85.0%, respectively. Nevertheless, 4 of 5 episodes of respiratory tract infection (bacterial, CMV, Aspergillus spp.) were similarly associated with cytokine mRNA. The ratios of IgG2 to IgG1, a reflection of Th1/Th2 influence, were not statistically different when analyzed for the presence or absence of ACR (0.91+/-0.53 vs. 1.02+/-0.70, respectively; p = NS). By analysis of FEV1 trends, expression of interferon gamma was associated with a greater and persistent decrement (deltaFEV1 pre: -0.265+/-0.78 liters, and post: -0.236+/-0.1161; mean +/- SE) than ACR in the absence of interferon gamma expression (+0.158 +/- +0.065 and +0.236+/-0.007 liters, respectively) (Student-Newman-Keuls, p<.05).

CONCLUSION

Our findings suggest that interferon gamma mRNA expression and ICAM-1 may be valuable in both the diagnosis and prognosis for lung allograft ACR. IL-10, a Th2 cytokine, was locally expressed both in the presence and absence of ACR. Expression of mRNA for interferon y in BAL and, to a lesser extent ICAM-1, were associated with increased lung allograft dysfunction. Whether BAL cytokine "immunosurveillance" would complement or possibly supplant a specific "histologic pattern" and thereby direct different therapies after lung transplantation, may be potentially rewarding areas of further investigation.

Flexible bronchoscopy in lung transplantation

Bronchoscopy plays an indispensable role in lung transplantation. It is an essential part of the evaluation of potential lung donors, and it is the pivotal procedure in the management of lung transplant recipients. Although advances in immunodiagnostic methods may ultimately lead to noninvasive tests to detect rejection, histology will be the standard for some time, and transbronchial biopsy will remain the procedure of choice. Furthermore, the usefulness of bronchoscopy in the diagnosis of pulmonary infection after lung transplantation is unlikely to be supplanted by any emerging technique.

Constrictive (obliterative) bronchiolitis: diagnosis, etiology, and a critical review of the literature

Constrictive bronchiolitis (CB) (or obliterative bronchiolitis) designates inflammation and fibrosis occurring predominantly in the walls and contiguous tissues of membranous and respiratory bronchioles, with resultant narrowing of their lumens. It differs from bronchiolitis obliterans-organizing pneumonia in its histopathology and clinical course. Most cases of CB occur in the setting of organ transplants, particularly lung and heart-lung transplants, but also in bone marrow transplants. Other bona fide cases are rare: infection, particularly viral infection, appears to be a well-documented precursor to CB in children, but not in immunocompetent adults. Constrictive bronchiolitis also has been reported in the course of rheumatoid arthritis, in certain other autoimmune diseases such as pemphigus vulgaris, after inhalation of toxic gases such as nitrogen oxide, after ingestion of certain drugs or medicinal agents such as Sauropus androgynous, and as a cryptogenic illness. Recent reports suggest that CB, as defined by clinical criteria (that is, bronchiolitis obliterans syndrome), is very common in lung allograft recipients who survive more than 5 years and, although it is associated with significant mortality, it also can be clinically stable. Furthermore, with the current practice of close monitoring of these patients, it appears that CB may now be diagnosed at an earlier stage, at which resolution, or at least stabilization of progression, is possible. A histopathologic diagnosis of CB in lung transplant and other patients may be difficult to make due to the patchy distribution of lesions, the technical difficulty in obtaining tissue in late lesions with extensive fibrosis, and the failure to recognize lesions. With regard to the last of these, in early stages of disease, CB may be subtle and easily missed in routine hematoxylin-eosin-stained specimens, while in advanced stages the disease may be equally difficult to diagnose if the patchy scarring in the lung is interpreted as nonspecific. The relative loss of bronchioles and the relationship of the scars to contiguous arteries should signal the need for elastic stains to look for the residual elastica of the bronchioles amidst the foci of fibrosis. Increasingly, clinical grounds, including pulmonary functions studies and high-resolution computed tomography findings, are proving to be relatively sensitive methods of detecting CB. Finally, the progressive airway destruction in chronic transplantation rejection appears to be a T-cell-mediated process. The "active" form of constrictive bronchiolitis, with attendant lymphocytic inflammation of the airways, likely precedes the "inactive" or scarred form of constrictive bronchiolitis.

Bronchiolitis obliterans: pathogenesis, prevention, and management

Increasing early success-post lung transplant has been tempered by the long-term development of histologic bronchiolitis obliterans (OB) or of the progressive airway obstruction which is called bronchiolitis obliterans syndrome (BOS). Multiple lines of evidence suggest that OB/BOS is due to an injury directed against the epithelial cells in the airways of the donor lung by the immune system of the recipient. Acute rejection is the strongest risk factor for the subsequent development of this process. Efforts to prevent or minimize acute rejection may reduce the prevalence of OB/BOS. Results of treatment with augmented immunosuppression have been disappointing but the treatment of complicating infections in the allograft can be beneficial. Multicenter studies are needed to assess the efficacy of new immunosuppressive agents in preventing or treating OB/BOS.

Mixed (neutrophil-rich) interstitial pneumonitis in biopsy specimens of lung allografts: a clinicopathologic evaluation

STUDY OBJECTIVES

Mixed interstitial pneumonitis (MIP), defined herein as a diffuse neutrophil-rich inflammatory infiltrate within the interstitial tissues, is an uncommon finding that is not a standard manifestation of acute or chronic rejection. This study examines the clinical significance of MIP in lung allograft recipients at St. Louis University Hospital.

DESIGN

We retrospectively reviewed surgical pathology reports from a selected 50-month period, and identified MIP reported in 13 transbronchial biopsy specimens in lung transplant recipients, representing 4.7% of all lung allograft biopsy specimens seen during this 4-year period. Biopsy specimens with MIP were examined to confirm the presence of a neutrophil-rich interstitial infiltrate and other associated histopathologic findings. The culture results, cytopathologic findings, and clinical charts of the affected patients were also reviewed.

MEASUREMENTS AND RESULTS

The detection of MIP at some point in a patient's posttransplant course was found to be associated with a significantly shorter (p < 0.01) survival, when compared to lung allograft recipients who did not show this finding. A total of seven lung allograft recipients (23% of total) showed MIP at some point in their posttransplant course. Four of the seven (57%) were actively smoking following lung transplantation, compared to 0 of 22 patients who did not show MIP. Six of the 13 MIP biopsy specimens were associated with positive cultures. In no case did MIP coexist with the conventional histologic patterns of acute or chronic rejection. MIP also did not correlate with levels of immunosuppressive therapy or with the incidence of rejection at other times in the patients' posttransplant courses.

CONCLUSIONS

We found no evidence that MIP represents an unusual form of acute or chronic rejection. Instead, it appears to represent a response to acute injury, similar to other injury patterns (hyaline membranes, organizing pneumonia) in transplant recipients. Exposure to tobacco smoke is likely to have played a role in the development of MIP in at least some cases. Because patients with MIP had a significantly shorter posttransplant survival, MIP may usefully identify lung allograft recipients at risk for an adverse outcome.