대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Cryptogenic organizing pneumonia (BOOP)

Radiologic Findings

Chest PA and CT show ill-defined ground-glass opacities in the whole lungs with centrilobular and peribronchial distribution. Minimal peribronchial fibrotic change suggests a chronicity of the lesions.
Thoracoscopic wedge resection of the left lower lobe was done and the histology revealed intraluminal fibrosis involving respiratory bronchioles, multiple fibrous plugs and interstitial lymphoplasma cell infiltration, which suggests cryptogenic organizing pneumonia (BOOP).

Brief Review

Cryptogenic organizing pneumonia (COP or BOOP) is a histologic description and not a specific diagnosis. BOOP is one of the more common causes of chronic interstitial lung disease. Etiologies of BOOP include toxic fume or dust inhalation (extrinsic allergic alveolitis), post infectious (mycoplasma, fungal, or viral), connective tissue disease, smoking, chronic graft-vs-host disease, organ transplantation, and drug toxicity (Amiodarone). BOOP has also been described in the contralateral lung following radiation therapy. Commonly an etiologic factor is not identified and the condition is idiopathic in up to 50% of cases.
Idiopathic BOOP is also referred to as "cryptogenic organizing pneumonia". Most cases of idiopathic BOOP occur in patients between the ages of 40 and 60 years and there is no sex predilection. Patients generally present with a history of a flu-like illness prodrome with a dry, non-productive cough that lasts 2 to 12 weeks, malaise, gradual dyspnea, and a low-grade fever. Pulmonary function studies usually demonstrate restrictive abnormalities. The diagnosis should not be made without biopsy confirmation. There is no response to antibiotics, but the process often has a good response to treatment with steroids. Relapses may occur following cessation of steroid therapy in about one-third of cases.
Imaging:
Chest radiograph: The radiologic manifestations of BOOP are those of an organizing pneumonia. On chest radiograph, there is bilateral patchy, peripheral alveolar infiltrates (organizing pneumonia) or ground glass opacities in over two-thirds of cases. The consolidations are predominantly subpleural in up to 50-60% of patients. Unilateral, focal, or lobar consolidations are seen less commonly. All lung zones may be affected. Diffuse small linear and nodular opacities are seen in 20-40% of cases. The disorder can progress to fibrosis, but honeycombing is usually absent. Effusions are noted in 10% of cases on plain film and adenopathy is not usually identified.
Computed tomography: On HRCT, subpleural, patchy, basilar dense consolidations (80%) with air bronchograms and/or ground-glass densities (60%) producing a pattern of mosaic attenuation are the characteristic findings (in up to 50% of affected patients, especially the immune compromised), but this finding is non-specific as it may also be seen in chronic infection (TB, MAI), sarcoidosis, alveolar cell carcinoma, lymphoma, and chronic aspiration. Large, peripheral areas of irregularly marginated mass-like consolidation have also been described and may be seen in up to 20% of cases. Peribronchial thickening is common. Centrilobular nodular densities ranging in size from 1 to 10 mm (sometimes larger), which may be well or poorly defined, may also be seen (30-50% of cases) and correlate with areas of organizing pneumonia. Adenopathy is more commonly noted by CT (25%) and effusion is found in up to 30% of cases. The presence of dense consolidations helps to distinguish BOOP from DIP, and fibrosis is also not observed in BOOP.

References

Keywords

Lung, Idiopathic interstitial pneumonia, COP, IIP,