Clinical diagnosis
Case 105
【Discussion】Pulmonary emphysema is defined as permanent enlargement of airspaces distal to the terminal bronchioles without fibrosis (1, 2). Although congenital emphysema is caused by alpha-1-antitrypsin deficiency, smoking is the far-most causative factor for emphysema. Smoking in the long period causes damage and destruction of alveolar walls which usually occur in the upper lung because of poor ventilation of smoke. Pulmonary emphysema is categorized morphologically into four types: centrilobular, panlobular, paraseptal and bullous emphysema (1, 2). In our cases, chest CT showed emphysema owning all type components (Figs 1 to 6).
Further, all our cases had combined pulmonary emphysema predominantly in the upper lobes and fibrosis in the lower lobes. It is crucial to differentiate smoking-related interstitial fibrosis (SRIF) from emphysema with usual interstitial pneumonia (UIP) because of the different survival: 5-year survival, 85.7 % in SRIF vs 40 % in emphysema with UIP (3).
Specific radiologic findings of UIP are subpleural, symmetric and homogeneous honeycombing with ground glass attenuation (GGA)/reticulation in the lower lobes (4-6). In addition, interstitial thickening, architectural distortion and bronchiectasis are found in UIP (4-6). Meanwhile, radiologic findings of SRIF include six factors: emphysema adjacent to honey comb area, subpleural sparing of honeycombing, asymmetric honey combing, inhomogeneous honeycombing, absence of GGA/reticulation and absence of honeycombing in the upper lobes (3). More than three of these findings are seen more likely SRIF. In short, radiologic findings on CT of SRIF are similar as those on CT of non-specific interstitial pneumonia (NSIP) (7) except the finding of emphysema adjacent to honey comb area (3).
In our cases, Case 1 had pan-lobular emphysema + symmetric, subpleural and homogeneous honeycombing accompanied with GGA (Fig. 1), and Case 5 had bullous emphysema + subpleural and symmetric honeycombing accompanied with reticulation in the lower lobe and presence of honeycombing in the upper lobe (Fig. 5), indicating two cases meets the criteria of emphysema with UIP. Meanwhile, Case 2 had paraseptal emphysema + asymmetric, non-homogeneous, absence of GGA/reticulation and absence of honeycombing in the upper lobes (Fig. 2), Case 3 had centrilobular and paraseptal emphysema + asymmetric and inhomogeneous honeycombing, absence of honeycombing in the upper lobe and absence of reticulation/GGA (Fig. 3), Case 4 had pan-lobular and para-septal emphysema + asymmetric and inhomogeneous honeycombing, absence of honeycombing in the upper lobe and absence of reticulation/GGA (Fig. 4), indicating that these three cases meet the criteria of SRIF.
Histologically, UIP had specific findings: fibroblast infiltration (large fibroblast foci), quilt-like fibrosis and honeycombing with least inflammation, indicating UIP is not caused by inflammation but some injury or else (4-6). Meanwhile SRIF had microscopically uniform thickening of alveolar wall by hyalinized collagen deposition like ropey bundles with local fibroblast foci, associated emphysema (3). Unfortunately, our cases did not receive histologic examination.
【Summary】
We present six cases with combined pulmonary emphysema and fibrosis (CPEF) in five and bullous emphysema in one. Based on the radiologic findings of the five cases with CPEF, two cases were diagnosed as pulmonary emphysema with UIP and three cases diagnosed as SRIF. We should keep in mind that the specific radiologic findings of UIP are subpleural, homogeneous and symmetric honeycombing with reticular/GGA in the lower lobes. This pattern progress from lower lobe to upper lobe accompanied with advancing. Meanwhile, radiologic findings of SRIP include emphysema (centrilobular, para-septal, pan-lobular, bullous) + three or more of the six CT findings of asymmetric honeycombing, inhomogeneous honeycombing, subpleural sparing, absence of honey combing in the upper lobes and absence of reticular/GGA in the lower lobe, indicative of radiologic findings of SRIF being that of NSIP + emphysema. Further, histologic findings of UIP include remarkable fibroblast focus, quilt-like fibrosis and honeycombing, while that of SRIF includes thickening of uniform alveolar wall, localized fibroblast foci, and ropey bundle with emphysema. Histologically, fibrosis pattern of SRIP is also similar as that of NSIP, but distinct in a point of accompanying emphysema.
【References】
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2018.5.23