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Thoracic Imaging |
1 Departments of Radiology (M.A.)
2 Internal Medicine (H.H., M.S.), National Kinki Chuo Hospital for Chest Disease, 1180 Nagasone-cho, Sakai City, Osaka 591-8555, Japan.
| Abstract |
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MATERIALS AND METHODS: CT scans in seven patients with interstitial lung disease and associated polymyositis-dermatomyositis were evaluated retrospectively. Six patients underwent sequential CT (follow-up range, 28 years; mean, 4.3 years). Histologic confirmation of pulmonary involvement was available in five patients.
RESULTS: The predominant finding on the initial CT scans in four patients was subpleural consolidation, which corresponded to bronchiolitis obliterans organizing pneumonia with or without coexistent chronic eosinophilic pneumonia. In most cases, consolidation improved with use of corticosteroid and/or immunosuppressive therapy; in two patients, however, consolidation evolved into honeycombing. In one patient, diffuse areas of ground-glass opacity and consolidation appeared rapidly during illness; this patient died of sudden, rapid deterioration. In one patient with subpleural linear opacities, parenchymal abnormalities slowly progressed, and linear opacities had evolved into honeycombing at 8-year follow-up. In one patient with histologically proved organizing diffuse alveolar damage, bilateral patchy areas of ground-glass opacity and consolidation were seen. In one patient, subpleural bands changed to subpleural lines on sequential CT scans.
CONCLUSION: CT provides an excellent demonstration of the lung changes in patients with interstitial lung disease and associated polymyositis-dermatomyositis.
Index terms: Dermatomyositis, 60.614 Lung, CT, 60.12111, 60.12118 Lung, interstitial disease, 60.917 Myositis, 60.614
| Introduction |
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The manifestation of pulmonary involvement in polymyositis-dermatomyositis can occur in three patterns (5): (a) acute onset of fever, dyspnea, and lung infiltrates; (b) insidious onset of dyspnea and diffuse interstitial fibrosis; and (c) abnormal chest radiographs without respiratory symptoms. Patients with interstitial lung disease of relatively acute onset appear to experience the most reliable and dramatic response to therapy with high doses of corticosteroids (5,6), whereas those with a more insidious onset of interstitial lung disease are less likely to show a quickly demonstrable response to corticosteroids (4,5). Some patients may have severe, progressive, and ultimately fatal lung involvement despite the use of corticosteroids and immunosuppressive agents (7,8).
The computed tomographic (CT) appearance of interstitial lung disease associated with polymyositis-dermatomyositis has been described (9); however, to our knowledge little has been reported about long-term follow-up CT evaluation. Recently, Mino et al (9) reported on CT images that showed pulmonary involvement in 19 patients with polymyositis or dermatomyositis. They reported findings of consolidation with a patchy and subpleural distribution, parenchymal bands, and irregular peribronchovascular thickening, which they deemed as being characteristic and reversible CT findings in patients with polymyositis or dermatomyositis.
The purpose of this study was to determine the long-term follow-up CT findings in seven patients with interstitial lung disease associated with polymyositis-dermatomyositis. Histologic confirmation of pulmonary involvement was available in five of these patients.
| MATERIALS AND METHODS |
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The study group consisted of three men and four women aged 4361 years (mean age, 52.9 years) at the time of the initial examination. Four patients had never smoked, and three patients had a history of smoking. Four patients developed pulmonary symptoms 960 months before they developed skin and muscular symptoms. Polymyositis-dermatomyositis preceded pulmonary symptoms by 2 weeks in one patient and by 4 weeks in another. One patient experienced a simultaneous onset of pulmonary and muscular symptoms; the mean interval between the onset of pulmonary symptoms and the onset of muscular symptoms in the other six patients was 22 months (range, 2 weeks to 60 months). Six patients underwent sequential CT examinations (mean, five CT examinations per patient; range, four to 10 examinations per patient) during a 28-year follow-up (mean follow-up, 4.3 years). After initial CT, all seven patients received corticosteroids, immunosuppressive agents, or both.
Thin-section CT was performed with a Quantex Plus CT unit (Yokogawa Medical System, Hino, Japan). All CT scans were obtained at maximal inspiration by using 2-mm collimation at 20-mm intervals. Scanning extended from the lung apices to below the costophrenic angles. Images were reconstructed with a high-spatial-frequency algorithm. CT scans were obtained with the patient in the supine position, and additional scans were obtained with the patient in the prone position when necessary to demonstrate the reversibility of high attenuation in dependent lung. All CT scans were obtained with window settings appropriate for lung parenchyma (window width, 1,500 HU; level, -700 HU) and mediastinum (window width, 300 HU; level, 10 HU).
The CT scans were evaluated independently and in random order by two observers who had no knowledge of the clinical and pathologic data, and the final assessment was achieved by consensus if there were disagreements in interpretation. The CT images were reviewed and coded repeatedly for the presence of each of the following signs: (a) ground-glass opacity, which was defined as an area of slightly increased attenuation in which the bronchi and vessels remain visible; (b) consolidation, which was defined as an area of increased attenuation with obscuration of the adjacent bronchial walls and vessels; (c) subpleural lines, which were defined as thin lines, 2 cm or longer, running parallel to the chest wall and within 1 cm of the pleural surface; (d) subpleural bands, which were defined as thick, bandlike opacities running parallel to the chest wall in a subpleural region; (e) traction bronchiectasis and bronchiolectasis, which were recognized on the basis of dilatation and an abnormal depiction of the airways in the peripheral portion of the lung, usually within the areas of increased attenu-ation or honeycombing; (f) linear opacity, which included septal and nonseptal lines; and (g) honeycombing, which was defined as an area of small cystic spaces less than 1 cm in diameter with thickened walls.
Parenchymal opacification on the entire CT scan was also assessed for laterality of involvement; focal, patchy, or diffuse distribution; predominantly central or peripheral localization; and upper, middle, or lower lung predominance. To assess changes that occurred over time, the CT scans in each patient were examined in sequence. The pattern, extent, and distribution of abnormal CT findings were compared with findings in the same region on previous and subsequent CT scans.
| RESULTS |
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Follow-up CT Findings
In all four patients with predominantly subpleural consolidation, the extent of consolidation decreased with use of corticosteroid therapy, immunosuppressive therapy, or both. In two patients with subpleural consolidation, one of whom was found to have coexistent chronic eosinophilic pneumonia and BOOP at open lung biopsy, sequential CT scans showed that the areas of consolidation evolved over time into honeycombing (Fig 1). In one patient with histopathologically proved BOOP, consolidation clearly disappeared on follow-up CT scans; after the cessation of therapy, however, nodular areas of ground-glass opacity appeared within the subpleural region. In one patient, diffuse ground-glass opacity and consolidation appeared rapidly 3 years after the consolidation had decreased due to the use of corticosteroid therapy (Fig 2c), and this patient died of respiratory failure within 2 weeks after this acute onset.
In the patient with subpleural linear opacities and ground-glass opacity, sequential CT scans showed that the areas of linear opacity evolved into honeycombing over a course of 8 years (Fig 3).
In the patient with subpleural bands, patchy consolidation, and small cystic spaces, the subpleural bands and patchy consolidation changed into subpleural lines and ground-glass opacity, respectively, on sequential CT scans. Small cystic lesions showed no change on sequential CT scans.
| DISCUSSION |
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Patients with interstitial lung disease associated with polymyositis-dermatomyositis can be classified into three groups on the basis of their symptoms at presentation (35): (a) those with an acute onset of symptoms, (b) those who present with more slowly progressive dyspnea on exertion, and (c) those without pulmonary symptoms but with abnormal chest radiographs or pulmonary function test results.
The histologic lesion underlying the relatively acute onset is that of diffuse alveolar damage or BOOP. In patients with diffuse alveolar damage, the prognosis is poor. BOOP is characterized by a good response to corticosteroids, however, and patients with this condition have an excellent prognosis. However, Epler et al (12) reported that patients with BOOP and a collagen vascular disease appeared to have a worse prognosis compared with patients with BOOP but no collagen vascular disease. In rare cases, death may result due to progressive disease (13). In the patients in our study, BOOP and chronic eosinophilic pneumonia in combination with BOOP progressed to honeycombing at sequential CT.
In patients with the more insidious onset of interstitial lung disease associated with polymyositis-dermatomyositis, varying degrees of usual interstitial pneumonia are found at histologic examination. Patients with usual interstitial pneumonia appeared to have a poorer prognosis than did those with BOOP. In some studies (5), however, prolonged corticosteroid therapy in most patients with chronic disease appeared to prevent or slow progression of disease. Wells et al (14) found that idiopathic pulmonary fibrosis and fibrosing alveolitis with systemic sclerosis have different courses and that survival in patients with fibrosing alveolitis and associated systemic sclerosis was substantially better than that in patients with idiopathic pulmonary fibrosis.
The CT findings of interstitial lung disease associated with polymyositis-dermatomyositis vary widely. The most common CT finding in our study was subpleural consolidation, which, in pathologic terms, corresponded to chronic eosinophilic pneumonia or BOOP. Most of the consolidation improved with therapy with corticosteroids, immunosuppressive agents, or both; in some cases, however, consolidation evolved into honeycombing. Schwartz et al (4) reported that some cases of BOOP may progress to usual interstitial pneumonia. Mino et al (9) reviewed CT scans that showed pulmonary involvement in 19 patients with polymyositis or dermatomyositis, and in 16 of the 17 patients who underwent sequential CT, consolidation improved greatly. In one of the 17 patients, progression of the CT abnormalities was observed, but honeycombing was not detected during the course of disease in any of the patients.
The CT findings of acute interstitial pneumonia are bilateral, symmetric areas of ground-glass opacity and consolidation (15). In one patient in our study, these CT findings of acute interstitial pneumonia were seen. Histopathologic examination of biopsy specimens in this patient showed organizing diffuse alveolar damage. These CT findings differed from those of the other patients studied, however, in that extensive areas of ground-glass opacity were observed, with no subpleural predominance.
In one patient in our study who had sudden acute deterioration, CT features of the new and advancing areas of ground-glass opacity and consolidation were similar to those of acute interstitial pneumonia. Tazelaar et al (11) described one patient with BOOP who developed adult respiratory distress syndrome in the immediate postoperative period; they also described three patients with usual interstitial pneumonia and associated polymyositis-dermatomyositis who deteriorated rapidly and died soon after open lung biopsy. The patient in our study had no inciting risk factor, such as surgical risk (ie, the patient did not undergo surgery). Akira et al (16) reviewed the CT findings in 17 patients with idiopathic pulmonary fibrosis that caused acute decompensation during the course of their otherwise chronic illness. They reported new and advancing areas of ground-glass opacity and consolidation that were found at CT during the acute exacerbation; autopsy results, which were available in seven patients, showed diffuse alveolar damage in addition to usual interstitial pneumonia.
As reported in the literature (25), there are many other causes of lung disease in patients with polymyositis-dermatomyositis. Some pulmonary manifestations are the result of aspiration secondary to dysphagia and muscle weakness. Aspiration, however, was not evident in any of the patients in our study.
In conclusion, CT findings of interstitial lung disease associated with polymyositis-dermatomyositis varied among the patients in our study. The most common CT finding was subpleural consolidation. In histopathologic terms, consolidation corresponded to BOOP or chronic eosinophilic pneumonia. In most cases, subpleural consolidation improved with corticosteroid and/or immunosuppressive therapy, but, in some cases, consolidation evolved into honeycombing. In some patients, acute decompensation may occur suddenly while the patient is in a stable state; therefore, long-term follow-up may be needed for these patients. In patients with both polymyositis-dermatomyositis and usual interstitial pneumonia, areas of ground-glass opacity progressed to honeycombing, as evidenced both histologically and radiologically. Patients with diffuse, patchy areas of ground-glass opacity and consolidation had a poor prognosis. Thin-section CT provided an excellent demonstration of the lung changes over time in patients with interstitial lung disease and associated polymyositis-dermatomyositis.
| Footnotes |
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Abbreviation: BOOP = bronchiolitis obliterans organizing pneumonia
Author contributions: Guarantors of integrity of entire study, M.A., M.S.; study concepts and design, M.A.; definition of intellectual content, M.A.; literature research, M.A.; clinical studies, M.A., H.H., M.S.; data acquisition and analysis, M.A., H.H.; manuscript preparation, editing, and review, M.A.
Received February 13, 1998;
revision requested May 5, 1998; revision received June 1, 1998;
accepted August 10, 1998.
| References |
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