Cyclophosphamide in severe steroid-resistant bronchiolitis obliterans organizing pneumonia

How I diagnose and treat organizing pneumonia in hematopoietic cell transplant recipients

ABSTRACT

Organizing pneumonia (OP) is a known noninfectious pulmonary complication following allogeneic hematopoietic cell transplant (HCT) and represents a significant risk factor for nonrelapse mortality in HCT recipients. Unlike bronchiolitis obliterans syndrome, it is not universally acknowledged as a distinctive pulmonary manifestation of chronic graft-versus-host disease (cGVHD) and, therefore, its diagnostic criteria and management approach are lacking. Given its shared similar clinical features and radiological and histologic findings to OP in the non-HCT population, the diagnostic approach and treatment strategy for OP in HCT recipients is largely adapted from the non-HCT population. In this article, we aim to enhance the understanding of OP within the context of cGVHD following HCT and distinguish its clinical features and treatment strategy from non-HCT counterparts, thereby reinforcing its recognition as a pulmonary manifestation of graft-versus-host disease. We will propose the diagnostic criteria and outline our approach in diagnosis and treatment strategy, highlighting the potential challenges that may arise in each process. Finally, we will discuss knowledge gaps in this field and identify the area of need for future research.

Noninfectious Pulmonary Complications after Hematopoietic Stem Cell Transplantation

Pulmonary complications after hematopoietic stem cell transplantation (HSCT) are important sources of morbidity and mortality. Improvements in infection-related complications have made noninfectious pulmonary complications an increasingly significant driver of transplantation-related mortality. Broadly, these complications can be characterized as either early or late complications, with idiopathic pneumonia syndrome and bronchiolitis obliterans syndrome the most prevalent early and late complications, respectively. Outcomes with historical treatment consisting mainly of corticosteroids are often poor, highlighting the need for a deeper understanding of these complications' underlying disease biology to guide the adoption of novel therapies that are being increasingly used in the modern era.

Rituximab for steroid-resistant organising pneumonia in a woman with rheumatoid arthritis

Organising pneumonia (OP) is a form of interstitial pneumonia characterised by inflammation and scarring leading to obstruction within the small airways and alveoli. Practice guidelines recommend treatment of moderate to severe OP with glucocorticoids; however, there have been cases of steroid-resistant OP successfully treated with rituximab. We describe a case of a woman in her 20s with rheumatoid arthritis who presented with pleuritic chest pain, haemoptysis and dyspnoea on exertion and was diagnosed with OP after multiple radiographic images and biopsies. The patient failed numerous treatment regimens, including corticosteroids, antibiotics and mycophenolate, but was successfully treated with rituximab. This case highlights the importance of identifying new therapeutic agents that will minimise the use of glucocorticoids in the treatment of OP.

Pulmonary Toxicities of Immunotherapy

Immune checkpoint inhibitors are a form of immunotherapy that are increasingly being used in a wide variety of cancers. Immune-related adverse events (irAEs) pose a major challenge in the treatment of cancer patients. Pneumonitis, the most common lung irAE, can cause significant disruptions in the treatment of cancer and may be life-threatening. The goal of this chapter is to instruct readers on the incidence and clinical manifestations of pneumonitis and to offer guidance in the evaluation and treatment of patients with pneumonitis.

A Case Report of Steroid-Resistant Cryptogenic Organizing Pneumonia Managed with Intravenous Immunoglobulins

Fewer than ten reported cases of cryptogenic organizing pneumonia (COP) have been managed with intravenous immunoglobulins (IVIg). We report a case of a 72-year-old man who presented with a worsening cough and diffuse opacities on chest radiograph. Following no improvement with antibiotics and negative complementary investigations for infectious, malignant, and autoimmune etiologies, COP was confirmed on lung biopsy. Due to continued clinical deterioration despite high-dose steroids and new severe steroid-induced hallucinations, the patient was placed on intravenous immunoglobulins (IVIg) and mycophenolate mofetil and made a satisfactory recovery. IVIg should be considered as an important steroid-sparing alternative in patients with COP.

Everolimus induced organizing pneumonia in a patient with tuberous sclerosis complex

Organizing pneumonia is characterized by a distinct histologic pattern in the lung interstitium and presents clinically as hypoxemia, fever, cough, and dyspnea that is not attributable to concurrent infection. Typical etiologies of this condition include inflammatory disease, malignancy, toxic inhalation, and an array of medications including the mTOR inhibitor everolimus. In this report, we describe the case of a female with tuberous sclerosis complex on everolimus therapy for renal angiomyolipomas who presented to the hospital with persistent cough, dyspnea, and fevers and bilateral lower lobe opacities on chest X-ray despite multiple courses of antibiotic therapy. Bronchoscopy was performed with transbronchial biopsies, and results demonstrated a lymphocytic predominance and pathologic findings of intraluminal plugs composed of fibroblasts and myofibroblasts consistent with organizing pneumonia. Everolimus therapy was discontinued and patient completed a steroid course with resolution of symptoms. To our knowledge, this is the first published case of organizing pneumonia secondary to everolimus in a patient with tuberous sclerosis complex.

Immune-Related Adverse Events: Pneumonitis

Checkpoint inhibitors are part of the family of immunotherapies and are increasingly being used in a wide variety of cancers. Immune-related adverse events pose a major challenge in the treatment of cancer patients. Pneumonitis is a rare immune-related adverse event that presents in distinct patterns. The goal of this chapter is to instruct readers on the incidence and clinical manifestations of pneumonitis and to offer guidance in the evaluation and treatment of patients with pneumonitis.

Pazopanib-induced organizing pneumonia in a patient with leiomyosarcoma: A case report

Pazopanib, a multityrosine kinase inhibitor used for treating malignant soft tissue tumors, rarely causes adverse events associated with the respiratory system. We report a case of a 73-year-old male with leiomyosarcoma treated with pazopanib. Four months after treatment initiation, chest computed tomography showed bilateral patchy consolidation and ground-glass opacities. Bronchoscopy revealed increased lymphocytes in the bronchoalveolar lavage fluid. Histological analysis of lung tissue demonstrated intraluminal fibrotic changes in alveolar spaces. According to these findings, we diagnosed the patient with pazopanib-induced organizing pneumonia. To best of our knowledge, this is the first report of such a case.

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Pazopanib is a multityrosine kinase inhibitor used for treating soft tissue tumors.

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Pazopanib rarely causes adverse events associated with the respiratory system.

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This is the first report of a patient with pazopanib-induced organizing pneumonia.

Successful treatment of three patients with organizing pneumonia associated with rheumatoid arthritis using clarithromycin and prednisolone

Macrolides have anti-inflammatory effects and have been used to treat diffuse panbronchiolitis, bronchiectasis, and cystic fibrosis. Lately, several cases of cryptogenic organizing pneumonia (COP) and radiotherapy-related organizing pneumonia (OP) that were successfully treated with macrolides considering their anti-inflammatory effects were reported. We report three cases of OP associated with rheumatoid arthritis (RA) successfully treated with clarithromycin (CAM) and prednisolone (PSL). Case 1: A 70-year-old woman suffering from RA was admitted with cough and severe dyspnea. She was diagnosed with OP associated with RA on the basis of computed tomography (CT) findings and transbronchial lung biopsy results. She was successfully treated with PSL and cyclosporine A. At the exacerbation of OP, she was successfully treated with CAM and PSL. Case 2: A 74-year-old man suffering from COP visited our department with arthralgia and articular swellings. He was diagnosed with RA, which was thought to be associated with OP. He was successfully treated with CAM and PSL. Case 3: A 54-year-old man suffering from RA presented with an exacerbation of arthralgia and articular swellings and cough. He was diagnosed with OP associated with RA on the basis of CT findings. He was successfully treated with CAM and PSL. The present cases suggest that CAM and PSL treatment may be effective in some cases of OP associated with RA.

Immune-Related Adverse Events: Pneumonitis

Checkpoint inhibitors are part of the family of immunotherapies and are increasingly being used in a wide variety of cancers. Immune-related adverse events pose a major challenge in the treatment of cancer patients. Pneumonitis is a rare immune-related adverse event that presents in distinct patterns. The goal of this chapter is to instruct readers on the incidence and clinical manifestations of pneumonitis and to offer guidance in the evaluation and treatment of patients with pneumonitis.

Nocardia brasiliensis Infection Complicating Cryptogenic Organizing Pneumonia

Pulmonary nocardiosis is a severe and uncommon opportunistic infection caused by Nocardia species. We present a patient with cryptogenic organizing pneumonia who was receiving long-term immunosuppressive therapy, whose treatment course was complicated by cutaneous and pulmonary nocardiosis. Tissue cultures confirmed Nocardia brasiliensis. Nocardiosis should be a diagnostic consideration for patients treated with long-term immunosuppression who have worsening pulmonary symptoms and relapsing pustular skin lesions.

A Cryptogenic Case of Fulminant Fibrosing Organizing Pneumonia

Cryptogenic organizing pneumonia (COP) generally responds well to corticosteroids with a favorable outcome. Rare cases of organizing pneumonia are rapidly progressive. Yousem et al. studied pathologic predictors of idiopathic bronchiolitis obliterans organizing pneumonia/COP with an unfavorable prognosis. Beardsley and Rassl proposed the name fibrosing organizing pneumonia (FOP). A 74-year-old female non-smoker presented with a 2-week history of dry cough followed by dyspnea and a fever. The clinical course was fulminant, but we successfully performed bronchoscopy. After the diagnosis of FOP, we treated the patient with mechanical ventilation and high-doses of steroids/immunosuppressants, which improved the disease.

[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 in patients with autoimmune rheumatic diseases

Bronchiolitis obliterans organizing pneumonia (BOOP) is defined by buds of granulation tissue within lung distal airspaces. The diagnosis requires the histopathologic evidence of organizing pneumonia along with a suggestive clinical and radiographic pattern. This disorder is characterized by a good response to corticosteroids and an excellent prognosis. It can occur in association with a broad spectrum of clinical conditions or can be isolated, in this last case named cryptogenic organizing pneumonia. We searched for BOOP in patients with autoimmune rheumatic diseases (ARD) in the literature, and we found 32 well-documented cases. We reported here demographic features, manifestations, treatment and outcome of patients with BOOP associated with ARD. Notably, BOOP can be the presenting feature in some patients with ARD; thus, a close follow-up of patients with BOOP is recommended.

Non-infectious respiratory disease in non-HIV immunocompromised patients

This review summarizes current knowledge regarding frequently encountered non-infectious respiratory complications in adult immunocompromised hosts (excluding those with human immunodeficiency virus (HIV) infection). In particular it will discuss complications of transplantation and of primary immunodeficiencies.

Organizing Pneumonias

Organizing pneumonia is a particular type of inflammatory and reparative reaction of the lung parenchyma characterized by fibroblast proliferation in the distal airspaces with overall preservation of the lung architecture. When microscopic, it is an asymptomatic and nonspecific reaction of little clinical significance accompanying many pathological processes. When macroscopic and affecting large portions of the lung parenchyma, it manifests by restrictive ventilatory defect and gas exchange impairment leading to dyspnea, cough, hypoxemia, alveolar opacities at chest imaging, and symptoms of systemic inflammation such as fever, malaise, and weight loss. This picture constitutes the clinico-pathological syndrome of organizing pneumonia, which has been recognized and characterized as a distinct entity in the past 30 years. Although the classical features of organizing pneumonia are increasingly familiar to chest physicians, and the efficacy of corticosteroid treatment makes it appear at first sight as an easy problem to resolve, atypical clinical presentations, similarities with other diseases, severe forms, histological variants, side effects of therapy, and relapses can make the management more difficult than initially expected. This chapter will address the classical and less common features of organizing pneumonia, and will provide practical clues to the diagnosis and management of this disorder.

Macrolides: from in vitro anti-inflammatory and immunomodulatory properties to clinical practice in respiratory diseases

BACKGROUND

Macrolides have long been recognised to exert immunomodulary and anti-inflammatory actions. They are able to suppress the "cytokine storm" of inflammation and to confer an additional clinical benefit through their immunomodulatory properties.

METHODS

A search of electronic journal articles was performed using combinations of the following keywords: macrolides, COPD, asthma, bronchitis, bronchiolitis obliterans, cystic fibrosis, immunomodulation, anti-inflammatory effect, diabetes, side effects and systemic diseases.

RESULTS

Macrolide effects are time- and dose-dependent, and the mechanisms underlying these effects remain incompletely understood. Both in vitro and in vivo studies have provided ample evidence of their immunomodulary and anti-inflammatory actions. Importantly, this class of antibiotics is efficacious with respect to controlling exacerbations of underlying respiratory problems, such as cystic fibrosis, asthma, bronchiectasis, panbrochiolitis and cryptogenic organising pneumonia. Macrolides have also been reported to reduce airway hyper-responsiveness and improve pulmonary function.

CONCLUSION

This review provides an overview on the properties of macrolides (erythromycin, clarithromycin, roxithromycin, azithromycin), their efficacy in various respiratory diseases and their adverse effects.

Temozolomide-associated bronchiolitis obliterans organizing pneumonia successfully treated with high-dose corticosteroid

Temozolomide is an oral alkylating agent with clinical activity against glioblastoma multiforme (GM). It is generally well-tolerated and has few pulmonary side effects. We report a case of temozolomide-associated brochiolitis obliterans organizing pneumonia (BOOP) requiring very high-dose corticosteroid treatment. A 56-yr-old woman presented with a 2-week history of exertional dyspnea. For the treatment of GM diagnosed 4 months previously, she had undergone surgery followed by chemoradiotherapy, and then planned adjuvant chemotherapy with temozolomide. After the 1st cycle, progressive dyspnea was gradually developed. Chest radiograph showed diffuse patchy peribronchovascular ground-glass opacities in both lungs. Conventional dose of methylprednisolone (1 mg/kg/day) was begun for the possibility of BOOP. Although transbronchial lung biopsy findings were compatible with BOOP, the patient's clinical course was more aggravated until hospital day 5. After the dose of methylprednisolone was increased (500 mg/day for 5 days) radiologic findings were improved dramatically.

Adjunctive effects of cyclosporine and macrolide in rapidly progressive cryptogenic organizing pneumonia with no prompt response to steroid

Cryptogenic organizing pneumonia (COP) generally responds well to corticosteroids with a favorable outcome. However, it can rapidly worsen and lead to respiratory failure that is refractory to corticosteroids. Adjunctive drugs have been used in refractory cases with various outcomes, but treatment experience is still lacking. We present a case of rapidly progressive COP accompanying air leak syndrome, which showed no prompt response to corticosteroids alone but gradual improvement with the addition of cyclosporine and macrolide. This case report supports the existing literature suggesting that an early therapeutic trial of this drug combination might be considered in COP patients whose condition worsens despite corticosteroid administration.

Consensus Conference on Clinical Practice in Chronic GVHD: Second-Line Treatment of Chronic Graft-versus-Host Disease

Steroid refractory chronic graft-versus-host disease (cGVHD) is associated with a significant morbidity and mortality. Although first-line treatment of cGVHD is based on controlled trials, second-line treatment is almost solely based on phase II trials or retrospective analyses. The consensus conference on clinical practice in cGVHD held in Regensburg aimed to achieve a consensus on the current evidence of treatment options as well as to provide guidelines for daily clinical practice. Treatment modalities are the use of steroids and calcineurin inhibitors as well as immunomodulating modalities (photopheresis, mTOR-inhibitors, thalidomide, hydroxychloroquine, vitamin A analogs, clofazimine), and cytostatic agents (mycophenolate mofetil, methotrexate, cyclophosphamide, pentostatin). Recent reports showed some efficacy of rituximab, alemtuzumab, and etanercept in selected patients. Moreover, tyrosine kinase inihibitors such as imatinib came into the field because of their ability to interfere with the platelet-derived growth factor (PDGF-R) pathway involved in fibrosis. An other treatment option is low-dose thoracoabdominal irradiation. Although different treatment options are available, the "trial-and-error system" remains the only way to identify the drug effective in the individual patient, and valid biomarkers are eagerly needed to identify the likelihood of response to a drug in advance. Moreover, the sparse evidence for most treatment entities indicates the urgent need for systematic evaluation of second-line treatment options in cGVHD.

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.

Cryptogenic organizing pneumonia

Cryptogenic organizing pneumonia is a rare, distinct disorder that is sufficiently different from the other diseases in the group of idiopathic interstitial pneumonias to be designated as a separate entity. In its most typical presentation, it is characterized by dyspnea and cough, with multiple patchy alveolar opacities on pulmonary imaging. Definite diagnosis is obtained by the finding of buds of granulation tissue in the distal airspaces at lung biopsy. No cause (as infection, drug reaction, or associated disease as connective tissue disease) is found. Corticosteroid treatment is rapidly effective, but relapses are common on reducing or stopping treatment.

Bronchiolar disorders

Bronchiolar abnormalities are relatively common and occur in a variety of clinical settings. Various histopathologic patterns of bronchiolar injury have been described and have led to confusing nomenclature with redundant and overlapping terms. Some histopathologic patterns of bronchiolar disease may be relatively unique to a specific clinical context but others are nonspecific with respect to either etiology or pathogenesis. Herein, we present a scheme separating (1) those disorders in which the bronchiolar disease is the predominant abnormality (primary bronchiolar disorders) from (2) parenchymal disorders with prominent bronchiolar involvement and (3) bronchiolar involvement in large airway diseases. Primary bronchiolar disorders include constrictive bronchiolitis (obliterative bronchiolitis, bronchiolitis obliterans), acute bronchiolitis, diffuse panbronchiolitis, respiratory bronchiolitis, mineral dust airway disease, follicular bronchiolitis, and a few other rare variants. Prominent bronchiolar involvement may be seen in several interstitial lung diseases, including hypersensitivity pneumonitis, respiratory bronchiolitis-associated interstitial lung disease, cryptogenic organizing pneumonia (idiopathic bronchiolitis obliterans organizing pneumonia), and pulmonary Langerhans' cell histiocytosis. Large airway diseases that commonly involve bronchioles include bronchiectasis, asthma, and chronic obstructive pulmonary disease. The clinical relevance of a bronchiolar lesion is best determined by identifying the underlying histopathologic pattern and assessing the correlative clinico-physiologic-radiologic context.

Thin-section CT in patients with severe acute respiratory syndrome following hospital discharge: preliminary experience

PURPOSE

To report the initial experience regarding thin-section computed tomographic (CT) findings in patients with severe acute respiratory syndrome (SARS) who improved clinically after treatment.

MATERIALS AND METHODS

Twenty-four patients (10 men, 14 women; mean age, 39 years; age range, 23-70 years) with confirmed SARS underwent follow-up thin-section CT of the thorax. The scans were obtained on average 36.5 days after hospital admission and were analyzed for parenchymal abnormality (ground-glass opacification, consolidation, or interstitial thickening) and evidence of fibrosis (parenchymal band, traction bronchiectasis, irregular interfaces). Patients were assigned to group 1 (with CT evidence of fibrosis) and group 2 (without CT evidence of fibrosis) for analysis. Patient demographics, length of hospital stay, rate of intensive care unit admission, peak lactate dehydrogenase level, pulsed intravenous methylprednisolone therapy, and peak opacification on chest radiographs were compared between the two groups.

RESULTS

Parenchymal abnormality was found in 96% (23 of 24) of patients and ranged from residual ground-glass opacification and interstitial thickening in group 2 (nine of 24, 38%) to fibrosis in group 1 (15 of 24, 62%). Patients in group 1 were older (mean age, 45 vs 30.3 years), had a higher rate of intensive care unit admission (27% [four of 15] vs 11% [one of nine]), more requirement for pulsed intravenous methylprednisolone (87%, [13 of 15] vs 67% [six of nine]), higher peak lactate dehydrogenase level (438.9 vs 355.6 U/L), and higher peak opacification on chest radiographs (estimated area, 14% vs 11%) than patients in group 2.

CONCLUSION

Pulmonary fibrosis may develop early in patients with SARS who have been discharged after treatment. Patients who are older and have more severe disease during treatment are more likely to develop thin-section CT findings of fibrosis.

Nonresolving or slowly resolving pneumonia

Given the variability in rate of radiographic resolution, it remains controversial to decide when to initiate an invasive diagnostic work-up for nonresolving or slowly resolving pulmonary infiltrates. In immunocompetent patients who present with classical features of CAP (i.e., fever, chills, productive cough, new pulmonary infiltrate), clinical response to therapy is the most important determinant for further diagnostic studies. Within the first few days, persistence or even progression of infiltrates on chest radiographs is not unusual. Defervescence, diminished symptoms, and resolution of leukocytosis strongly support a response to antibiotic therapy, even when chest radiographic abnormalities persist. In this context, observation alone is reasonable, and invasive procedures can be deferred. Serial radiographs and clinical examinations dictate subsequent evaluation. In contrast, when clinical improvement has not occurred and chest radiographs are unchanged or worse, a more aggressive approach is warranted. In this setting, we advise fiberoptic bronchoscopy with BAL and appropriate cultures for bacteria, legionella, fungi, and mycobacteria. When endobronchial anatomy is normal and there is no purulence to suggest infection, TBBs should be done to exclude noninfectious causes (discussed earlier) or infections attributable to mycobacteria or fungi. An aggressive approach is also warranted in patients who are clinically stable or improving when the rate of radiographic resolution is delayed. As discussed earlier, what constitutes excessive delay is controversial, and depends upon the acuity of illness, specific pathogen, extent of involvement (i.e., lobar versus multilobar), comorbidities, and diverse host factors. Stable infiltrates even 2 to 4 weeks after institution of antibiotic therapy does not mandate intervention provided patients are improving clinically. Invasive techniques can also be deferred when unequivocal, albeit incomplete, radiographic resolution can be demonstrated. Lack of at least partial radiographic resolution by 6 weeks, even in asymptomatic patients, however, deserves consideration of alternative causes (e.g., endobronchial obstructing lesions, or noninfectious causes). Fiberoptic bronchoscopy with BAL and TBBs has minimal morbidity and is the preferred initial invasive procedure for detecting endobronchial lesions or substantiating noninfectious causes. The yield of bronchoscopy depends on demographics, radiographic features, and pre-test likelihood. In the absence of specific risk factors, the incidence of obstructing lesions (e.g., bronchogenic carcinomas, bronchial adenomas, obstructive foreign body) is low. Bronchogenic carcinoma is rare in nonsmoking, young (< 50 years) patients but is a legitimate consideration in older patients with a history of tobacco abuse. Non-neoplastic causes (e.g., pulmonary vasculitis, hypersensitivity pneumonia, etc.) should be considered when specific features are present (e.g., hematuria, appropriate epidemiologic exposures). Ancillary serologic tests or biopsies of extrapulmonary sites are invaluable in some cases. In rare instances, surgical (open or VATS) biopsy is necessary to diagnose refractory or non-resolving "pneumonias."