Abstract Organizing pneumonia (OP) is a reversible diffuse interstitial lung disease resulting from alveolar wall injury followed by an inflammatory and fibroproliferative reaction. Cryptogenic organizing pneumonia (COP) is the idiopathic form, typically resembling infectious pneumonia but defined by its responsiveness to systemic glucocorticoid therapy. Imaging findings are variable but often show peripheral patchy air-space opacities, ground-glass or nodular opacities with bronchial dilation and thickening. Secondary OP occurs with identifiable causes such as infection, drug toxicity, connective tissue disease (CTD), or malignancy. We present a case of COP in a previously healthy man with progressive respiratory symptoms unresponsive to antibiotics. A 50-year-old male never-smoker with prior myocarditis of unclear etiology initially presented to another facility with presumed community-acquired pneumonia, was treated with antibiotics, and discharged on home oxygen. His symptoms persisted, prompting re-evaluation one month later. HRCT chest revealed extensive multifocal dense and ground-glass opacities bilaterally. Bronchoscopy with BAL was non-diagnostic for infection. Given his non-toxic appearance, an inflammatory etiology was suspected. He denied new medications, significant occupational exposures (aside from prior auto repair work), or extrapulmonary symptoms of CTD. Rheumatologic evaluation showed a positive ANA but negative specific antibodies. Surgical lung biopsy via video-assisted thoracoscopic surgery (VATS) demonstrated organizing pneumonia. He was started on oral glucocorticoids with marked improvement within two weeks, was weaned off oxygen, and had near-resolution of CT findings after two months. At a multidisciplinary interstitial lung disease (ILD) conference, pathology raised limited concern for non-specific interstitial pneumonia (NSIP) features; however, given the absence of CTD evidence, the diagnosis of COP was confirmed. Three months after cessation of steroids, he experienced symptomatic and radiographic relapse. COP is a rare, enigmatic interstitial lung disease requiring histopathologic confirmation, exclusion of secondary causes, and multidisciplinary discussion for definitive diagnosis. This case underscores the central role of multidisciplinary evaluation and the necessity for close longitudinal follow-up. Standard treatment involves systemic glucocorticoids, typically prednisone for 4-6 months with gradual taper, resulting in resolution in approximately two-thirds of patients. Non-responders warrant reassessment for alternate diagnoses or secondary causes and may require second-line immunosuppressive therapy such as azathioprine or mycophenolate. Relapses are common, as in this patient. Given the known association of OP with CTD and NSIP patterns, ongoing surveillance remains essential for early identification of evolving connective tissue disease. Figure 1. Fibroblastic Plug (Masson Body) This abstract is funded by: None
Pascual et al. (Fri,) studied this question.