Idiopathic bronchiolitis obliterans organizing pneumonia. Definition of characteristic clinical profiles in a series of 16 patients

Bronchiolitis obliterans organizing pneumonia (BOOP) is a pathologic finding common to various injuries to the lung of either definite or idiopathic etiology. Since the presentation of patients with idiopathic BOOP varies, we studied 16 patients with BOOP on pulmonary histology to define more distinct and homogeneous clinical and imaging profiles of idiopathic BOOP. We distinguished three groups of patients: group 1 (n = 4), with multiple patchy migratory pulmonary involvement of the pneumonia type. Their clinical course was subacute, with cough, fever, weight loss, mild dyspnea, and increased ESR. Chest x-ray film and CT scan showed multiple alveolar opacities. All patients completely recovered with corticosteroid therapy but relapsed when therapy was stopped too rapidly. Group 2 (n = 5) had solitary pulmonary involvement of the pneumonia type occurring in a similar clinical context. Since carcinoma was suspected, they underwent surgical excision of the pneumonic area and recovered without relapse. Group 3 patients (n = 7) presented with diffuse pulmonary involvement of the interstitial lung disease type. They had more progressive onset of more severe dyspnea, crackles heard over all lung surfaces, and interstitial opacities with or without alveolar opacities on chest imaging. Improvement with corticosteroid therapy was obtained in only three patients. In all three groups, lung function test results showed a restrictive pattern. The obstructive pattern characteristic of pure bronchiolitis obliterans was found in none. BAL showed a mixed pattern (increase of both lymphocytes and polymorphonuclear cells) in the patients of the first two groups. Thus, we distinguished three characteristic clinical and imaging profiles in patients with idiopathic BOOP: multiple patchy pneumonia, solitary pneumonia, and diffuse interstitial lung disease. These profiles are so different that they should be distinguished in clinical studies of idiopathic BOOP.     

Two cases of bronchiolitis obliterans organizing pneumonia, showing multiple infiltrative shadows, diagnosed by open lung biopsy, and a report of their BAL findings

Two cases of bronchiolitis obliterans organizing pneumonia (BOOP) were diagnosed by clinical features and pathological findings of open lung biopsy specimens. Findings of repeated (bronchoalveolar lavage (BAL) fluid analysis were also reported. Case 1 was a 54 year-old woman complaining of dry cough and low grade fever. Multiple infiltrative shadows in both lung fields were pointed out on her chest roentgenogram. Case 2 was a 68 year-old woman with symptoms of cough, sputum and low grade fever. Her chest X-ray films also showed multiple infiltrative shadows bilaterally. Although various antibiotics were given to both patients, new shadows appeared on their chest films without any improvement of clinical symptoms or inflammatory findings. TBLB specimens obtained from the two cases showed the findings of organizing pneumonia. In each case, open lung biopsy was performed, and the pathological diagnosis was consistent with BOOP. However, exclusion of the possibility of eosinophilic pneumonia and lymphoproliferative disorders of the lung was somewhat difficult in case 1. BALF analysis showed an increased number of lymphocytes in both cases, 75% and 37% respectively. The inverted ratio of OKT4/OKT8 (0.71) in BALF of case 1 was similar to that of hypersensitivity pneumonitis. In spite of clinical and roentgenological improvement after steroid therapy, the abnormal BAL findings still remained. Therefore it is suggested that BAL may be a useful tool for monitoring the steroid treatment of patients with BOOP.     

Bronchiolitis obliterans organizing pneumonia (BOOP) in Japan

Twenty-nine patients with bronchiolitis obliterans organizing pneumonia (BOOP) in Japan diagnosed by an open lung biopsy were reviewed. A total of 70% of the patients were idiopathic and 2/3 of the remaining were associated with connective tissue disease. All 29 cases of BOOP showed bilateral pulmonary infiltration on chest X-rays. BOOP can be classified based on the chest X-ray findings into three major types, Type I, Type II and unclasSified type. In Type I shadows appear in the lung fields. In Type II abnormal shadows are seen in the bi-basilar peripheral field with the reduction of the lung volume. Cases of Type I showed inflammatory findings more frequently than cases of Type II. Among 29 BOOP patients, two idiopathic cases died.     

Clinico-pathological study of collagen-related pulmonary lesions in cases of open lung biopsy]

We studied the clinico-pathological correlation of collagen disease-related pulmonary lesions to examine the pathological and radiological features of collagen lung, and the effect of steroid therapy. Ten open lung biopsy cases were examined; 4 male, and 6 female. The mean age was 55 years old. Seven cases developed pulmonary shadows after the diagnosis of collagen disease, and 3 cases showed pulmonary shadow prior to diagnosis. Pathologically, 6 cases proved to be bronchiolitis obliterans organizing pneumonia (BOOP), 3 cases were chronic interstitial pneumonia (UIP), and 1 case was acute interstitial pneumonia. All cases had inflammatory thickening of the interstitium involving the pleura, bronchial wall, and perivascular connective tissue. Half of the cases had bronchiolar inflammatory lesions. Radiologically BOOP cases showed either localized ground glass shadows, or diffuse reticulonodular shadows predominantly in the lower lung fields with shrinkage of affected areas. UIP cases showed reticulonodular shadows, and active UIP cases showed overlapping ground glass shadows. Steroids were administered in cases of BOOP and active UIP, and all cases showed improvement. We consider that open lung biopsy is of use in the diagnosis of some cases and in assessing whether steroid therapy is indicated.     

Interleukin 5 and granulocyte-macrophage colony-stimulating factor levels in bronchoalveolar lavage fluid in interstitial lung disease.

The purpose of this study was to evaluate the role of several eosinophil growth factors including interleukin (IL)-5, interleukin (IL)-3 and granulocyte-macrophage colony-stimulating factor (GM-CSF) in the pathogenesis of interstitial lung disease with eosinophilia. IL-5, IL-3 and GM-CSF in bronchoalveolar lavage fluid (BALF) were measured by enzyme-linked immunosorbent assay (ELISA) in patients with eosinophilic pneumonia (EP), bronchiolitis obliterans organizing pneumonia (BOOP), idiopathic pulmonary fibrosis (IPF), sarcoidosis and healthy volunteers. IL-5 in BALF was high only in patients with EP. IL-3 in BALF was undetectable in the majority of patients with these diseases. GM-CSF in BALF was detectable in 30-67% of each group of patients. In patients with BOOP and IPF, the number of eosinophils in BALF was higher in patients with detectable GM-CSF than in patients in whom GM-CSF was below the detection limit. Eosinophil cationic protein (ECP) was detected in all patients with EP and some with BOOP and IPF. There was a significant correlation between ECP levels and percentage or number of eosinophils in BALF. The results suggest the possibility that interleukin 5 in eosinophilic pneumonia, and granulocyte-macrophage colony-stimulating factor in bronchiolitis obliterans organizing pneumonia and idiopathic pulmonary fibrosis may play important roles in eosinophil recruitment in the lung. Activation of eosinophils in the lung is likely to be induced by both interleukin 5 and granulocyte-macrophage colony-stimulating factor.     

BALF cell findings in patients with BOOP, particularly in comparison with UIP

It is possible to differentiate to some degree to bronchiolitis obliterans organizing pneumonia (BOOP) of unknown etiology from idiopathic usual interstitial pneumonia (UIP) on the basis of clinical symptoms, chest X-ray findings, pulmonary function test and blood gas findings, but in certain patients it can be difficult. Cell findings in bronchoalveolar lavage fluids (BALF) were compared between 8 patients with BOOP and 28 patients with UIP, both diagnosed histologically by open lung biopsy. Findings characteristic of BOOP included (1) an increase in the percentage of lymphocytes, (2) an increase in the percentage of eosinophils, and (3) a decrease in the OKT4+/OKT8+ ratio. These findings provide useful information in making a clinical diagnosis of BOOP and in evaluating proper steroid treatment in patients who unable to undergo open lung biopsy.     

An unusual case of bronchiolitis obliterans organizing pneumonia concomitant with bronchioloalveolar carcinoma

Although bronchiolitis obliterans organizing pneumonia (BOOP) has been associated with a variety of underlying disorders, the majority of cases of BOOP are idiopathic. We present the case of a 61-year-old patient with fever, dry cough, bilateral patchy consolidation and high erythrocyte sedimentation rate. Open lung biopsy shows coexistence of BOOP and bronchioloalveolar carcinoma. It is interesting that both diseases are predominantly air space diseases and present similar radiologic features making the diagnosis and follow-up of treatment more difficult.     

经支气管镜肺活检对弥漫性肺实质疾病的诊断价值

目的 评价经支气管镜肺活检(TBLB)在弥漫性肺实质病变诊断中的作用.方法 回顾性分析2001年1月至2006年10月在北京协和医院住院、经TBLB检查且具有完整临床资料的肺部弥漫性疾病患者416例,男157例,女259例,平均年龄(42.6±18.9)岁.结果 416例中124例(29.8%)经支气管镜肺活检确诊,其中结节病52例(41.9%),闭塞型细支气管炎伴机化性肺炎(BOOP/OP)28例(22.6%),肺泡蛋白沉积症(PAP)19例(15.3%),肺部肿瘤12例(9.7%),肺血管炎5例(4.0%),肺结核3例(2.4%),肺孢子菌肺炎、曲霉肺炎、嗜酸细胞肺炎、淋巴管肌瘤病(LAM)及肺淀粉样变各1例.经支气管镜肺活检未确定诊断的患者中104例进行了开胸或胸腔镜活检,98例确诊,其中非特异性间质性肺炎37例(37.7%),寻常型间质性肺炎18例(18.4%),结节病11例(11.2%),BOOP/OP 6例(6.1%),肿瘤5例(5.1%),外源性过敏性肺泡炎4例(4.1%),曲霉肺炎、PAP、淋巴细胞间质性肺炎、肺动脉高压及LAM各2例(各占2.0%),结核、肺血管炎、组织细胞增生症X、呼吸细支气管炎伴间质性肺炎、脱屑性间质性肺炎、弥漫性泛细支气管炎、气道中心性纤维化各1例(各占1.0%).结论 TBLB可对约30%的肺部弥漫性肺疾病确诊,可作为开胸之前的常规筛查手段.     

How are interstitial lung diseases diagnosed in Germany? Results of the scientific registry for the exploration of interstitial lung diseases ("Fibrosis registry") of the WATL

From 1995 to 1999 we evaluated questionnaires sent by pulmonologists and departments of pulmonology in order to register interstitial lung diseases. On the whole 1142 patients (579 males, 563 females, mean age 51.1 +/- 15.3 years, sarcoidosis, n = 511, extrinsic allergic alveolitis, n = 145, idiopathic pulmonary fibrosis, n = 308, bronchiolitis obliterans organizing pneumonia (BOOP), n = 93, others, n = 85) were recorded in the registry. With reference to the mean age sarcoidosis occurred most frequently in the fourth decade and idiopathic pulmonary fibrosis in the sixth decade. In all these diseases bronchoscopy with bronchoalveolar lavage and transbronchial biopsy was predominantly used for further diagnosis. It was striking that high-resolution computed tomography of the thorax was still rarely used when diagnosing these diseases. Apart from the group with BOOP the number of non-smokers in men and women was decisively higher than the average of the population of Germany.     

Idiopathic bronchiolitis obliterans organizing pneumonia (idiopathic BOOP) in childhood

Idiopathic bronchiolitis obliterans organizing pneumonia (idiopathic BOOP) is a clinicopathological entity of unknown origin first described by Epler and colleagues in 1985. We report our findings from a study of two Japanese boys aged 12 and 13 years with idiopathic BOOP. The patients showed no respiratory symptoms nor signs of infection. There was no history of exposure to noxious agents or medications in either case. Laboratory data, including hematological, biochemical, and immunological tests, were normal, and pulmonary function tests showed only a slight nonprogressive decrease from normal predicted values in vital capacity and diffusing capacity. Serial radiographs in both cases showed migration of patchy infiltrates. Fiberoptic bronchoscopy was performed for evaluation of eosinophilic pneumonia, but the bronchoalveolar lavage (BAL) revealed no increase in eosinophils and a decrease in CD4/CD8 ratio in the BAL fluid. Histopathological findings of transbronchial lung biopsy (TBLB) specimens were compatible with a diagnosis of BOOP. As neither case has shown clinical abnormalities apart from migratory patchy infiltrates on chest radiographs, both patients have been observed without drug therapy for 3–4 years. Pediatr Pulmonol. 1996; 22:67–72. © 1996 Wiley-Liss, Inc.     

Bronchiolitis obliterans organizing pneumonia. Clinical and roentgenological features in 26 cases

BACKGROUND: Bronchiolitis obliterans organizing pneumonia (BOOP) may be classified as cryptogenic (idiopathic) and secondary. There are no clear clinical and radiological features distinguishing between idiopathic and secondary BOOP. OBJECTIVES: To analyze the etiologic factors, clinical and radiological features, diagnostic approach and response to therapy at onset and outcome in subjects with BOOP. METHODS: The medical files of Erciyes University Hospital from 1995 to 2003 were retrospectively reviewed. Patients with biopsy-proven BOOP were selected for evaluation. The etiology and initial features of BOOP, treatment, resolution, relapse, and survival were obtained from medical records, and a follow-up patient questionnaire. RESULTS: We have diagnosed 26 cases (13 males /13 females) with BOOP syndrome (mean age 54 +/- 15 years, range 14-93). More than half the patients (58%) were classified as idiopathic BOOP. Patients presented with cough (92%), dyspnea (70%), pleuritic chest pain, hemoptysis and fever (50%). The biopsy specimens had been obtained by transbronchial and/or transthoracic lung biopsy in 18 cases (69%). At radiological evaluation, there were bilateral patchy alveolar and/or interstitial infiltrates in 16 patients (62%), and solitary pneumonic involvement in 10 patients (38%). Three patients recovered spontaneously, 5 remained cured after resection of the focal lesion. Corticosteroid therapy was given in 17 patients (65%). Apart from four patients who died (death was attributable to BOOP in only 1 patient) and three patients who relapsed, the prognosis was good in all patients. CONCLUSIONS: The etiology of BOOP is usually idiopathic. We observed that hemoptysis and pleuritic chest pain were a relatively frequent symptom in BOOP in the present series, in contrast to previous observations. The diversity of radiological and clinical presentations including hemotysis and pleuritic chest pain should prompt consideration of the diagnosis in patients with persisting pulmonary symptoms and radiological findings.     

Utility of fiberoptic bronchoscopy in nonresolving pneumonia

Although fiberoptic bronchoscopy (FOB) has been traditionally used to evaluate nonresolving pneumonia, its efficacy is unknown. We, therefore, reviewed FOB in 35 consecutive patients who had (1) a roentgenographic infiltrate, (2) cough, (3) either temperature greater than 38.1 degrees C, leukocytosis, sputum production, (4) symptoms present for at least ten days, and antibiotic therapy for at least one week. Known lung cancer and AIDS were excluded. Fiberoptic bronchoscopy was diagnostic in 86 percent (12/14) in whom a specific cause was found. No patient had endobronchial cancer. Two patients with nondiagnostic FOB and persistent systemic symptoms had open lung biopsy specimens showing Wegener's granulomatosis and bronchiolitis obliterans with organizing pneumonia (BOOP). Twenty-one patients with nondiagnostic FOB had no final diagnoses other than community-acquired pneumonia. We conclude that FOB is extremely useful in finding a specific diagnosis for a nonresolving pneumonia when a specific diagnosis can be made. Fiberoptic bronchoscopy was most likely to yield a specific diagnosis in nonsmoking patients with multilobar infiltrates of long duration and could have been avoided in older, smoking, or otherwise compromised patients with lobar or segmental infiltrates with no decrease in diagnostic yield in our series.     

Granulomatous Pneumocystis carinii pneumonia in Wegener's granulomatosis.

This study reports on a first case of granulomatous Pneumocystis carinii pneumonia (PCP) in a human immunodeficiency virus-negative patient with antineutrophil cytoplasmic antibody-positive Wegener's granulomatosis whilst receiving immunosuppressive treatment. The patient presented with diffuse alveolar haemorrhage, pauci-immune rapid progressive glomerulonephritis and leukocytoclastic vasculitis of the skin. Granulomatous Pneumocystis carinii pneumonia developed under immunosuppressive treatment with cyclophosphamide and prednisone. At the time Pneumocystis carinii pneumonia developed, there was a marked lymphopenia with a very low CD8+ cell count in the blood. Grocott staining in bronchoalveolar lavage fluid revealed no Pneumocystis carinii. The diagnosis was made via a video-assisted thoracoscopic lung biopsy which showed granulomas containing high numbers of Pneumocystis carinii cysts.     

Correlations of histologic classification with clinical features and prognosis in interstitial lung disease associated with collagen disease]

We studied 32 patients with interstitial pneumonia associated with collagen disease. All underwent surgical lung biopsy. Twenty-seven were histologically classified as follows: 8 with usual interstitial pneumonia (UIP), 10 with nonspecific interstitial pneumonia (NSIP), 6 with bronchiolitis obliterans organizing pneumonia (BOOP), and 3 with diffuse alveolar damage (DAD). Twenty-five of the patients were treated with corticosteroid but 4 (3 DAD, 1 NSIP) deteriorated rapidly and died within a month after lung biopsy. At the final follow-up, all 8 UIP patients were alive with residual respiratory impairment, whereas 6 NSIP and 4 BOOP patients had almost completely recovered. These findings suggested that histologic classification can be highly valuable to the therapeutic responsiveness and prognosis in cases of interstitial pneumonia associated with collagen disease.     

A limited form of Wegener's granulomatosis with bronchiolitis obliterans organizing pneumonitis-like variant in an ulcerative colitis patient

A case of a 19-year-old man with ulcerative colitis (UC) developed multiple pulmonary nodular shadows with cavity formation, elevated perinuclear antinuclear cytoplasmic antibody (pANCA) and positive lymphocyte stimulation test by drug (DLST) for mesalazine suggesting mesalazine induced Wegener's granulomatosis (WG). Transbronchial biopsy specimens were consistent with WG and thoracoscopic biopsy specimens were consistent with bronchiolitis obliterans organizing pneumonitis (BOOP). We diagnosed WG with BOOP-like variant, which was induced by mesalazine. To our knowledge, this is the first report of a limited form of WG associated with orally administered mesalazine.     

A comparative study of the prognosis for Japanese patients with idiopathic interstitial pneumonia or BOOP based on histopathologic subsets]

We explored the prognosis for 123 patients with either idiopathic interstitial pneumonia (IIP) or bronchiolitis obliterans organizing pneumonia (BOOP). All patients underwent either open lung biopsy or thoracoscopic lung biopsy procedures. The histopathologic diagnosis of IIP included patients with usual interstitial pneumonia (UIP), nonspecific interstitial pneumonia (NSIP), and desquamative interstitial pneumonia with respiratory bronchiolitis-associated interstitial lung disease. The prognosis was poorest for patients with a histologic diagnosis of UIP, and excellent for those who received a diagnosis of BOOP. Although the prognosis is generally considered to be good for patients with NSIP, some NSIP patients in our study died. Histopathologic diagnosis based on surgical lung biopsy is useful in evaluating the prognosis for patients with IIP.     

Influenza A-associated bronchiolitis obliterans organizing pneumonia mimicking Wegener's granulomatosis

We describe a patient with bronchiolitis obliterans organizing pneumonia (BOOP) requiring respiratory support and treated with corticosteroids and cytoxan for presumed Wegener's granulomatosis (WG). The diagnosis of WG was based on clinical presentation and strongly positive stains for anti-neutrophilic cytoplasmic antibodies (cANCA). The results of an open-lung biopsy were consistent with BOOP. Although BOOP has previously been described as one of the pulmonary manifestations of WG, other more specific histologic features of WG such as capillaritis or necrotizing vasculitis were lacking. Because influenza A virus was cultured from the patient's lung tissue, final assessment of the illness focused on this as the etiologic agent triggering the pulmonary syndrome. The presence of ANCA was considered to be nonspecific. The patient's condition improved with appropriate therapy for BOOP.     

Non-infectious and unusual infectious mimics of community-acquired pneumonia

Noninfectious or unusual infectious diseases may present with clinical, radiological and laboratorial characteristics of community-acquired pneumonia (CAP). Usually their presence is only suspected after treatment failure, leading to inappropriate interventions, unnecessary costs and risks related to the untreated potentially life-threatening disease. The present study aimed to assess the noninfectious or unusual infectious diseases that may be misdiagnosed as CAP that progresses with treatment failure. Sixteen hospitalized patients with presumptive diagnosis of CAP and treatment failure were described. The most prevalent symptoms were fever and cough. Radiological pattern of air-space disease was observed in 10 (62%) patients. The diagnosis was established by autopsy (12%) or invasive procedures (88%), as follows: open lung biopsy (nine), flexible fiberoptic bronchoscopy (two), transthoracic fine needle aspiration (two) and bone marrow aspiration (one). Eight patients had noninfectious diseases: pulmonary embolism, cryptogenic organizing pneumonia, Wegener's granulomatosis, hypersensitivity pneumonitis, bronchocentric granulomatosis, neoplastic disease and acute leukemia. The unusual infectious diseases were: tuberculosis, cryptococcosis, actinomycosis, histoplasmosis and paracoccidioidomycosis. Patients with noninfectious or unusual infectious diseases may present with symptoms and radiological findings that mimic CAP. These diseases should always be suspected in patients who do not respond to initial empirical antimicrobial treatment, especially young patients or those without comorbidity.     

Bronchiolitis obliterans-organizing pneumonia: an Italian experience

The purpose of this study was to describe the clinical features at onset and outcome and the diagnostic approach in subjects with bronchiolitis obliterans-organizing pneumonia (BOOP). Over a 7-year period we observed 78 cases of biopsy-proven bronchiolitis obliterans-organizing pneumonia, in which well documented clinical and radiographic data were available. The final diagnosis of BOOP was validated when patients presented: (i) negative microbiological analysis on BAL fluid; (ii) a well documented improvement either spontaneous, or after steroid treatment or (iii) cases with progressive respiratory failure and increasing radiographic shadows, an open lung biopsy or autopsy that excluded other entities. There were 42 males and 36 females; the mean age was 61+/-12 years (range 12-85 years). Forty-two (54%) patients were current smokers, 25 (32%) had never smoked and 11 (14%) were ex-smokers. The clinical pattern at presentation of BOOP was more frequently similar to classical acute or sub-acute infectious pneumonia. Fever (63%), dyspnoea (58%) and dry cough (53%) were the typical symptoms on admission. A flu-like syndrome preceeding BOOP was observed in 21 cases (27%). Inspiratory crackles (78%) were the most typical finding at physical examination. However, 13% of the patients were asymptomatic and an abnormal chest X-ray film was the reason for seeking medical attention. Radiographically the most frequent pattern of BOOP was a unilateral consolidation (44%) with lower field predominance. A migratory behaviour was present in 22% of the cases. High-resolution computed tomographic (HR-CT) scan when performed, was more sensitive in detecting ground glass infiltrates, sub-pleural or peri-bronchovascular distribution or the presence of nodules or cavitation. Most patients (68%) were classified as having idiopathic BOOP. However, the same clinical-roentgenological pattern was observed in patients after radiotherapy for ductal breast carcinoma (6%), in collagen-vascular diseases (6%), related to drugs (9%), to infections serologically documented (4%), and to graft vs. host disease (4%). Four patients (all of whom had idiopathic BOOP) presented a rapid progressive respiratory failure needing mechanical ventilation. In another two cases respiratory failure appeared after a long period during which patients experienced exertional dyspnoea and low grade fever. BAL profile was characterized by lymphocytosis with a reduction of the CD4/CD8 ratio, associated with a slight increase of neutrophils and eosinophils and scattered mast cells. However in two cases we had an increased CD4/CD8 ratio and in one case the presence of a significant 12% of polyclonal B cells. In a few cases atypical (cytokeratin-positive cells) epithelial cells were detected: these cells were constantly present in the BAL fluid of patients with rapidly progressive respiratory failure. From the diagnostic point of view this series documents that transbronchial lung biopsy (coupled with BAL) can be the first diagnostic step. However, therapy can be started on the basis of BAL data (when a characteristic morphological and phenotypical profile is evident) in cases in which the clinical presentation is suggestive and a biopsy cannot be made. Most patients showed a rapid and good response to steroid therapy. However, three patients died (4%) in spite of steroid therapy (two cases) and steroid and cyclophosphamide therapy (one case). In conclusion, although clinical findings, chest X-ray film and CT Scan findings usually suggest the diagnosis a definite confirmation requires transbronchial lung biopsy and BAL and, less frequently, open lung biopsy.     

Bronchiolitis obliterans organizing pneumonia in Korea

Abstract An analysis of the clinical features in 23 cases of bronchiolitis obliterans organizing pneumonia (BOOP) in Korea is presented. Six were men and 17 were female, with a male-tofemale ratio of 1:2.4. Idiopathic BOOP was present in 18 of these patients, connective tissue disease-associated BOOP in five and all of them were females. The most frequent symptoms were dyspnoea and coughing in both groups; and crackles were the most prominent physical findings. Leukocytosis was observed in seven of the idiopathic BOOP group and all in the connective tissue disease-associated BOOP group. In most cases, FVC, FEV¹, diffusing capacity and arterial O₂ pressure were reduced. In roentgenographic study, patchy air space consolidation was the major finding and subpleural predominance was observed in the majority of patients in both groups. Migration of lesions were identified in only two patients with idiopathic BOOP. Steroid treatment was effective in all of idiopathic BOOP. In contrast to previous reports, an analysis of the 23 Korean BOOP patients showed several interesting points. First, a female predominance was observed. Second, migration of lesion was rare. Third, it did not show any different prognosis in patients with reticular pattern on roentgenogram compared with patients with patchy air space consolidation on roentgenogram. Whether these differences were due to ethnic or environmental factors is to be determined.