British Journal of Radiology 74 (2001),189-191 © 2001 The British Institute of Radiology
Non-specific interstitial pneumonia showing a "crazy paving" pattern on high resolution CT
E Coche, MD
1
B Weynand, MD
2
P Noirhomme, MD
3 and
T Pieters, MD
4
1 Departments of Radiology
2 Pathology
3 Surgery
4 Pneumology, Cliniques Universitaires St-Luc, Avenue Hippocrate 10, 1200 Brussels, Belgium
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Abstract
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Non-specific interstitial pneumonia is characterized pathologically by uniform interstitial inflammation and fibrosis. This disease is most commonly demonstrated on high resolution CT as subpleural ground-glass opacity mixed with irregular linear opacities. The authors report a case of non-specific interstitial pneumonia with high resolution findings consistent with a "crazy paving pattern". This appearance, represented by smoothly thickened interlobular septa with a background of geographic areas of ground-glass opacity, is unusual for non-specific interstitial pneumonia and was indistinguishable from other interstitial or alveolar lung diseases.
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Introduction
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The patient was a 47-year-old woman who presented with persistent non-productive cough of several weeks duration, moderate dyspnoea and weakness, but no fever. She smoked ten cigarettes a day. Right basilar inspiratory crackles were heard on chest auscultation. The erythrocyte sedimentation rate was 25 mm h-1, the C-reactive protein level was 4 mg dl-1 and the carcinoembryonic antigen level was 5.3 ng ml-1 (normal value in our institution <3 mg ml-1). A chest radiograph showed ill defined consolidation in the right lower lobe (Figure 1
). Antibiotic therapy with clarithromycine (500 mg day-1) had been given for 15 days without significant clinical improvement. A chest radiograph 1 month later showed extension of the right basilar consolidation and a subtle ground-glass opacity at the left lung base. High resolution CT (HRCT) was performed (Figure 2) at full inspiration. Areas of ground-glass opacity were present in both lower lobes, with a geographic distribution, in addition to smoothly thickened interlobular septa. Lung function tests demonstrated normal lung volumes and diffusion capacity. Bronchoalveolar lavage yielded clusters of atypical epithelial cells with irregular nuclei. The cytological appearances were equivocal and compatible with a well differentiated adenocarcinoma. Surgical biopsy was performed and histological examination of the pulmonary parenchyma showed a uniform picture, with alveolar septal thickening due to inflammatory cells and proliferating fibroblasts. Atypical Type II pneumocytes were present (Figure 3). The diagnosis was consistent with non-specific interstitial pneumonia. The patient completely recovered clinically and radiographically after a 3 month course of methylprednisolone (8 mg). There was no relapse 9 months after diagnosis.
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Figure 1. Posteroanterior chest radiograph at time of onset of symptoms shows patchy consolidation in the right lower lobe.
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Figure 2. (a) High resolution CT (lung windows), 15 days after Figure 1 , show geographic areas of ground-glass opacification associated with smoothly thickened interlobular septa (arrows) in both lower lobes. This appearance is called the "crazy paving" pattern. (b) The same abnormalities were present in the right middle lobe (arrow).
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Figure 3. Lung biopsy: the pulmonary parenchyma is homogeneously affected. Interalveolar septa are thickened by an inflammatory infiltrate and only slight fibrosis (haematoxylin and eosin, magnificationx43).
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Discussion
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Non-specific interstitial pneumonia (NSIP) is a relatively new entity among diffuse interstitial idiopathic pulmonary diseases. NSIP is characterized pathologically by uniform interstitial inflammation and fibrosis appearing over a short period of time; NSIP is characterized clinically by a generally good prognosis [1]. This temporal uniformity of the parenchymal changes seen in NSIP contrasts greatly with the normally temporal heterogeneity of usual interstitial pneumonia (UIP). UIP represents a specific histological pattern of fibrosing interstitial pneumonia, seen in the majority of patients with idiopathic pulmonary fibrosis, and is generally considered to be a fatal disorder. The radiographic and HRCT appearances of NSIP have recently been described [2–5]. NSIP with fibrosis is most commonly seen on HRCT as a patchy subpleural area of ground-glass opacity mixed with irregular linear opacities or bronchial dilatation, with lower zone predominance [3]. Nishiyama et al [5] found ground-glass opacity and consolidation on HRCT in 15 patients with NSIP. In this study, linear and reticular opacities were always associated with traction bronchiectasis. In our case, ground-glassopacities on HRCT were distributed in a geographic fashion and were combined with smoothly thickened interlobular septa within areas of air space disease. No bronchial dilatation was present. This appearance, which has been called the "crazy-paving" pattern in the radiological literature, was initially considered to be strongly suggestive of alveolar proteinosis [6] and was later described in lipoid pneumonia and mucinous bronchioloalveolar carcinoma [7, 8]. Some investigators [9] have shown that the "crazy paving" pattern is a non-specific finding seen in a variety of interstitial and air space lung diseases. NSIP has not previously been included in the spectrum of diseases with a "crazy paving" appearance. Cottin et al [10], in a recent study of 12 consecutive patients with NSIP, reported the juxtaposition of pulmonary segments involved and uninvolved by ground-glass opacity. There was abnormal thickening of the interlobular septa in five patients, but the authors do not specify whether there was superimposition of interlobular thickening with ground-glass opacities. This HRCT pattern reflects the underlying pathological findings present in our case. Ground-glass opacities may represent interstitial thickening caused by inflammation and active fibrosis. Smoothly thickened interlobular septa may represent alveolar septal thickening with pneumocyte hyperplasia, inflammation and minimal fibrosis. This appearance corresponds to the cellular interstitial pneumonia described in the Group 1 patients of Katzenstein et al [1]. A decrease of ground-glass opacities has been reported on follow-up CT scans [4], with improvement of pulmonary function tests in this group of patients treated with corticosteroids. The paucity of thick collagen fibres in our patient may explain the complete recovery of the lung appearances without any residual lung changes on CT following treatment.
Received for publication May 15, 2000.
Revision received September 8, 2000.
Accepted for publication September 25, 2000.
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References
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Abstract
Introduction
