Reticulation and centrilobular branching linear structure corresponded histopathologically to UIP and bronchiolitis obliterans, respectively. Consolidation corresponded to COP with or without findings of coexistent chronic eosinophilic pneumonia. Reticulations deteriorate rapidly especially when they are associated with the new appearance of multifocal areas of GGO. Centrilobular branching linear structures show a tendency to progress to bronchiectasis. Consolidation shows a tendency to improve in one half of patients and to evolve into HC in the remaining half at serial CT.

Interstitial lung changes are frequent and independent of disease duration. Interstitial changes are more frequent and severe in rheumatoid factor-positive patients and in patients with more severe joint involvement [14].

Progressive Systemic Sclerosis (PSS)

Pulmonary involvement is more common and more severe in PSS than in other types of collagen vascular disease. The most common pulmonary manifestations are interstitial fibrosis, which occurs in approximately 80 % of patients [15]. Pulmonary fibrosis is equally likely in limited and diffuse diseases but is less severe in the limited form [16].

At autopsy, some degree of parenchymal interstitial fibrosis is frequent. The histologic features are those of NSIP or UIP pattern (Fig. 28.5). Follicular bronchiolitis is seen occasionally. Although COP pattern may be associated with a variety of CVDs, there are rare reports of bronchiolitis associated with scleroderma [1]. DAD has often been recognized rarely in association with PSS [17].

TSCT frequently demonstrates the evidence of interstitial pneumonitis and fibrosis in patients who have normal or questionable radiographic findings [18]. The abnormalities involve mainly the lower lung zones and have a predominant peripheral and posterior distribution [19]. In a recent study by Kim et al. [20], serial TSCT findings were correlated with the results of pulmonary function tests in 40 patients with PSS and interstitial pneumonia. The overall extent of disease and extents of HC and GGO increased significantly on follow-up CT. Both forced vital capacity and forced expiratory volume in 1 s decreased significantly in the follow-up examination. The increase in the extent of HC on CT correlated significantly with the decrease in diffusing capacity for carbon monoxide. The rate of progression of HC in patients with idiopathic UIP is a mean of 0.4 % of lung volume in a month [21]. According to a study [20], the progression rate of HC in PSS is 0.07 % of lung volume in a month.

Polymyositis (PM) and

Dermatomyositis (DM)

The thorax is commonly affected in PM or DM, generally in one or more of three forms: (a) hypoventilation and respiratory failure as a result of involvement of the respiratory muscles; (b) interstitial pneumonitis (usually with a histologic pattern of UIP or NSIP) (38); and (c) aspiration pneumonia secondary to pharyngeal muscle weakness (probably the most common pulmonary complication) [1, 22].

Interstitial lung disease associated with PM–DM has a wide spectrum of histopathologic features. Three major groups can be identified on the basis of histologic patterns: COP, UIP/NSIP (Fig. 28.6), and DAD (Fig. 28.7) patterns. Histologic appearance is useful for determining patient prognosis. Patients with DAD or UIP pattern show poor prognosis with only a 33 % survival rate at 5 years [1, 23]; however, patients with COP pattern have excellent prognosis. Patients with NSIP pattern have good prognosis.

Initial TSCT findings of pulmonary involvement in patients with PM–DM are prominent interlobular septa, GGO, patchy consolidation, parenchymal bands, irregular peribronchovascular thickening, and subpleural lines. HC may be seen in up to 16 % of patients who have abnormal chest radiographs or pulmonary function [24]. Areas of consolidation with or without GGO correspond histopathologically to COP or organizing DAD pattern. Patchy consolidation, parenchymal bands, and irregular peribronchovascular thickening improve on sequential CT, becoming pleural irregularities and prominent interlobular septa, GGO, and subpleural lines on follow-up CT scans [25]. Therefore, consolidation with patchy and subpleural distribution, parenchymal bands, and irregular peribronchovascular thickening are reversible. Occasionally, areas of GGO with parenchymal bands or subpleural lines representing pathologic area of UIP pattern may progress to HC [26].

Sjögren’s Syndrome

The most common thoracic complications of Sjögren’s syndrome are LIPs (Fig. 28.8) and airway abnormalities such as follicular bronchitis, bronchiectasis, and bronchiolitis. Less common complications include interstitial pneumonitis and fibrosis (Fig. 28.9), COP, lymphoma, pulmonary hypertension, and pleural effusion or fibrosis [27].

Pathologically, LIP is characterized by a diffuse, usually bilateral, interstitial infiltration of lymphoplasma cells [1]. It is usually most prominent in relation to bronchioles and their accompanying vessels but can be seen in the alveolar interstitium. Fibrosis is usually mild [28].

Fig. 28.5 Interstitial fibrosis of usual interstitial pneumonia pattern in a 59-year-old woman with progressive systemic sclerosis. (a, b) Lung window of CT scans (3.0-mm section thickness) obtained at levels of bronchus intermedius (a) and liver dome (b), respectively, show patchy and extensive areas of reticulation and ground-glass opacity in both lungs. (c) Coronal reformatted image (3.0-mm section thickness) demonstrate similar pattern of reticulation and ground-glass opacity extensively in both lungs. (d) Low-magnification (×4) photomicrograph of

surgical lung biopsy specimen obtained from right lower lobe exhibits dense fibrosis along interlobular septum (arrows) and around bronchiole (open arrow). (e) High-magnification (×100) photomicrograph depicts dense fibrosis in interlobular septum (arrows) and around bronchiole (open arrows). Also note thick fibrotic vessel wall (arrowheads). (f) High-magnification (×200) photomicrograph discloses area of focal active fibrosis (arrow)

Fig. 28.6 Pulmonary fibrosis of nonspecific interstitial pneumonia pattern in a 48-year-old woman with polymyositis (PM)–dermatomyositis (DM). (a, b) Lung window of CT scans (2.5-mm section thickness) obtained at levels of right inferior pulmonary vein (a) and liver dome (b), respectively, show patchy areas of mixed ground-glass opacity and reticulation in bilateral lower lung zones. (c) Low-magnification (×4) photomicrograph of surgical lung biopsy specimen obtained from right

lower lobe demonstrates temporally and regionally homogeneous pulmonary fibrosis and chronic inflammatory cell infiltration with uniform alveolar wall thickening. There is no architectural distortion. Also note interstitial aggregates of lymphoid follicle (arrows). (d) Highmagnification (×100) photomicrograph discloses diffuse uniform widening of interstitium due to fibrosis and chronic inflammatory cell infiltration. Also note absence of architectural distortion

In a prospective study [29] dealing with TSCT findings of lungs in 50 consecutive patients, lung abnormalities were detected in 17 patients (34 %) on CT as compared with in 7 (14 %) patients on chest radiographs. The most common findings consisted of bronchiolectasis and poorly defined centrilobular small nodular or branching linear opacities (seen in 11 patients), areas of GGO (in 7), and HC (in 4). Areas of HC or both HC and GGO suggesting pulmonary fibrosis were bilateral and asymmetric and present almost exclusively in the periphery of the lower lobes [30]. A characteristic pattern of extensive areas of GGO with scattered thin-walled cysts is seen in approximately 50 % of patients with LIP [28, 31]. Similar findings have been described in LIP not associated with Sjögren’s syndrome [28]. Interstitial peribronchiolar lymphoplasmacytic infiltrates associated with overinflation of the secondary pulmonary lobule in

histopathologic specimens suggest that at least some of the cysts may be related to air trapping secondary to bronchiolar stenosis [32]. Poorly defined centrilobular small nodules and thickening of the bronchovascular bundles also seen in LIP represent expansion of the interstitial tissue by lymphoplasma cell infiltration [28].

Mixed Connective Tissue Disease

The term “mixed connective tissue disease” (MCTD) refers to a condition in which patients have mixed features of SLE, PSS, and PM. Respiratory involvement has been described in 20–80 % of patients. Common pulmonary abnormalities include interstitial pneumonitis and fibrosis, pulmonary hypertension, and pleural effusion.

Fig. 28.7 Diffuse alveolar damage in a 43-year-old woman with poly- myositis–dermatomyositis. (a, b) Lung window of CT scans (2.5-mm section thickness) obtained at levels of aortic arch (a) and liver dome (b), respectively, show patchy areas of consolidation in both lungs. Also note bilateral pleural effusions. (c) Low-magnification (×4) photomicrograph of surgical lung biopsy specimen obtained from left lower

lobe demonstrates diffuse widening of alveolar walls and edematous thickening of interlobular septa. (d) High-magnification (×100) photomicrograph highlights alveolar wall thickening with interstitial fibroblastic proliferation. Note some intra-alveolar fibrin and few inflammatory cells

Fig. 28.8 Lymphocytic interstitial pneumonia in a 63-year-old woman with Sjögren’s syndrome. (a, b) Lung window of CT scans (2.5-mm section thickness) obtained at levels of bronchus intermedius (a) and liver dome (b), respectively, show patchy areas of ground-glass opacity

harboring internal reticulation. Surgical biopsy specimen disclosed interstitial lymphocytic infiltration, finding compatible with lymphocytic interstitial pneumonia in Sjögren’s syndrome