Cryptogenic organising pneumonia

Clinical History

Patient with one month history of fever, cough and dyspnoea, who had undergone several courses of different antibiotherapy agents without response. Physical examination showed hypoxaemia and focal sparse crackles in the base of the left lung. Laboratory showed leukocytosis, neutrophilia and elevated levels of C-reactive protein.

Imaging Findings

Chest radiograph shows bilateral patchy consolidations (Figure 1a).
High-resolution CT of the thorax showed several areas of peripheral and peribronchovascular consolidation, with air bronchograms, sparing the subpleural space, predominantly involving the middle and lower lobes bilaterally, but also the upper lobes (Figure b-e). There is also ectasia and thickening of the bronchial walls. There are areas of ground glass opacities around the areas of parenchymal consolidation (Figure b-e). Serial radiographic and clinical features were consistent with organizing pneumonia and corticosteroid treatment was initiated. Our patient showed rapid improvement after starting corticotherapy, with apirexia in the same day. She underwent 6 months of treatment without symptoms (Figure 2). When the dose of corticosteroids was progressively reduced, a relapse occurred (Figure 3) and a new course of treatment was performed (Figure 4). She had no cause known to induce secondary organizing pneumonia.

Discussion

Cryptogenic organizing pneumonia (COP) is an idiopathic interstitial pneumonia with characteristic clinical and radiologic features. Some diseases (collagen vascular diseases, infections, malignancies) and drug reactions may induce similar findings (secondary organizing pneumonia (OP) [1-4]. OP is considered a non-specific response to lung injury. Histopathologically there is patchy distribution of intra-alveolar buds of granulation tissue, mild interstitial chronic inflammation, with preserved lung architecture [1-3, 5]. Mean age at onset is 55 years, there is no association with gender or cigarette smoking. Symptoms are nonspecific (cough, mild dyspnea, fever, flulike illness) with few weeks of evolution. Patients typically report a respiratory tract infection preceding their symptoms, and previous antibiotic treatments that fail [1-6]. High-resolution CT is indicated in virtually all patients suspected to have idiopathic interstitial pneumonias.
Typical imaging features of COP consist of bilateral patchy areas of air-space consolidation, with or without ground-glass opacities, with a tendency to progress, change location over time or regress spontaneously. The distribution is predominantly peripheral and inferior. Air bronchograms and bronchial dilatation may be present in consolidated areas [7].
Less common imaging features need to be recognized so that the diagnosis will not be overlooked. These include focal organizing pneumonia that may resemble lung cancer, nodular patterns, bronchocentric distribution, linear and band-like opacities forming arcades, perilobular pattern, and a progressive, irreversible fibrotic form [7].
The diagnosis should be confirmed with biopsy. However, when serial radiographic and clinical features are sufficiently characteristic, biopsy confirmation may be obviated [7] and corticosteroid treatment started. Rapid improvement reinforces the probability of COP. The final diagnosis is of exclusion of other causes of organizing pneumonia [1-5]. Patients show excellent response to corticosteroids with rapid clinical and imaging improvement. Patients recover without significant sequelae, however relapses are common within 3 months after stopping or reduction of corticosteroids, often leading to prolonged treatment [1, 3, 5]. The prognosis is good, as relapses do not appear to be associated with increased mortality or long-term morbidity. However, patients that show the progressive fibrotic pattern have a poorer prognosis [5, 7].

Differential Diagnosis List

Final Diagnosis

Cryptogenic organising pneumonia

URL:	https://www.eurorad.org/case/10483
DOI:	10.1594/EURORAD/CASE.10483
ISSN:	1563-4086