Cryptogenic Organizing Pneumonia with a Rare Radiographic Presentation of a Diffuse Micronodular Pattern Mimicking Miliary Lung Infiltration: A Case Report and Review of the Literature

Abstract

We reported a case of cryptogenic organizing pneumonia (COP) presenting with an unusual diffuse micronodular pattern (DMP) mimicking miliary lung infiltration. The patient is a 66-year-old man with a past medical history of diabetes mellitus type 2 and hyperlipidemia who presented with progressive dyspnea associated with significant weight loss and night sweats for 2 weeks. Upon admission, the patient’s clinical condition rapidly progressed to respiratory failure requiring mechanical ventilation. Initial Chest X-ray (CXR) showed diffuse reticulonodular infiltration mimicking miliary pattern. Chest computed tomography (CT) showed diffuse centrilobular micronodular infiltrations with features of a tree-in-bud pattern consistent with the CXR findings. He was then started on empiric antibiotics for community-acquired pneumonia and underwent a diagnostic bronchoscopy with alveolar lavage and transbronchial biopsies, which yielded negative cultures and unrevealing pathology. Tissue from CT-guided lung biopsy performed later on was also inconclusive. Due to the lack of clinical improvement, he eventually underwent surgical lung biopsy. The pathology result showed organizing pneumonia (OP) pattern with heavy lymphoplasmacytic infiltrates and numerous multinucleated giant cells. His final culture results, microbiological data and serology workup for autoimmune disease were all unremarkable. The patient was diagnosed with COP and was started on systemic corticosteroids. He displayed dramatic clinical improvement and was successfully liberated from the ventilator. Subsequent chest imaging showed resolution of the reticulonodular infiltrations. Early diagnosis for OP and ability to distinguish OP from infectious pneumonitides are critical as the majority of patients with OP respond promptly to corticosteroids. Common findings of radiographic pattern for OP are patchy air space consolidation or ground-glass opacity, yet DMP is another rare radiographic pattern that must be recognized, especially in COP. In summary, this case illustrates a rare radiographic presentation of COP. With early recognition and prompt diagnosis, proper treatment can significantly prevent morbidity and reduce mortality.

Reply to Takimoto: Micronodular Pattern of Organizing Pneumonia or Hypersensitivity Pneumonia Induced by an Immune Checkpoint Inhibitor?

“…In addition, the prevalence of a micronodular pattern of OP (MNOP) on radiological series is estimated to range from 10% to 24%; 4 however, the prevalence of a diffuse pattern in the total lung field of MNOP is rare. 4,5 CT pattern resembling HP has occasionally been observed in patients with immune checkpoint inhibitor (ICI)-induced pneumonia and described as centrilobular nodules, Copyright © 2020 by the American Thoracic Society bronchiolitis-like appearance, and tree-in-bud micronodularity; 6 however, the manifestation of diffuse pattern in the total lung fields of patients with ICI-induced pneumonia is rare. To the best of our knowledge, histopathological study of ICI-induced pneumonia with HP-like CT pattern has not been reported.…”

“…If these features are not detected, a surgical lung biopsy should be considered; however, small biopsy specimens are sufficient for diagnosis. In addition, the prevalence of a micronodular pattern of OP on radiological series is estimated to range from 10% to 24% ( 4 ); however, the prevalence of a diffuse pattern in the total lung field of micronodular pattern of OP is rare ( 4 , 5 ).…”

Examining Miliary Disease Etiology in a Coccidioides-Endemic Center: A Retrospective Cohort Study

“…Various metastatic cancers and other neoplastic processes are known causes of miliary disease [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Several interstitial lung diseases can present atypically with a miliary pattern, such as sarcoidosis [21], pulmonary alveolar microlithiasis [22], various pneumoconioses [23], hypersensitivity pneumonitis [24], lipoid pneumonia [25], vaping-associated lung injury [26], drug-induced pneumonitis [27], and organizing pneumonia [28]. Miscellaneous causes of miliary disease include multifocal micronodular pneumocyte hyperplasia [29] and pulmonary hemosiderosis due to mitral stenosis [30].…”

Micronodular Pattern of Organizing Pneumonia or Hypersensitivity Pneumonia Induced by an Immune Checkpoint Inhibitor?

“…OP, cryptogenic or secondary, is a clinicopathological entity characterized by granulation tissue plugs in the lumen of small airways, alveolar ducts, and alveoli. An unusual radiological presentation corresponding to diffuse micronodular pattern mimicking miliary lung infiltration has been reported, and the prevalence of this micronodular pattern of OP (MNOP) in radiological series is estimated to range from 10% to 24% ( 2 , 3 ). The typical MNOP on CT imaging is widespread lung micronodules without diffuse ground-glass opacities, airspace consolidation, or cavitation.…”