A43-23 Unmasking the Miliary Mirage: An Unusual Face of Cryptogenic Organizing Pneumonia

Abstract Introduction Cryptogenic organizing pneumonia (COP) is a rare form of idiopathic interstitial pneumonia of unknown insult characterized pathologically by intra-alveolar fibroproliferation which is often reversible with immunosuppressive therapy. It has a male predominance with a mean age of 50-60 years. Clinical presentation is often sub-acute with flu-like symptoms reported in 10-15% of cases, associated with dyspnea, fever and a dry cough. Variable radiographic patterns may be seen with the most common being peripheral predominant bilateral patchy airspace consolidative or ground glass opacities that are often migratory in nature. A diffuse micronodular pattern (DMP) has been less commonly reported. Herein, we present a case of COP in a 65 year old male who presented with flu like symptoms, progressively worsening shortness of breath and was subsequently found to have a diffuse micronodular pattern on CT imaging. Case Presentation 65 year old male current smoker with a 35 pack year smoking history presented with a 1 week history of flu like illness and progressively worsening shortness of breath. He denied recent travel, new medications, inhalational exposures or exposure to birds. He was initially hypoxic requiring supplemental oxygen and was found to have a diffuse micronodular pattern on Computed Tomography (CT) imaging with scattered consolidative opacities noted bilaterally (Figure 1). Azithromycin and Ceftriaxone were started empirically. Infectious workup was overall negative, Hypersensitivity Pneumonitis panel was unrevealing. Autoimmune workup was negative. He underwent bronchoscopy with bronchoalveolar lavage (BAL) that revealed negative viral, bacterial and fungal cultures and negative Acid Fast bacilli (AFB). Endobronchial Ultrasound (EBUS) and Transbronchial biopsy (TBB) performed revealed intraalveolar aggregates of fibroblasts suggestive of COP. He was started on corticosteroids at 1mg/kg which was slowly tapered with mycophenolate mofetil later added given intolerable corticosteroid effects. He was weaned off oxygen and continues to improve radiographically and symptomatically. Discussion A miliary micronodular pattern is characterized by the presence of innumerable randomly distributed micronodules measuring less than 3mm. When encountered, more common diagnoses such as tuberculosis, fungal infections and metastatic disease should be entertained. In COP, a miliary micronodular pattern is seen in 9-24% of cases. In our patient’s case, tuberculosis and other infectious etiologies were ruled out, biopsy was suggestive of COP and the patient was immediately started on corticosteroids with a good clinical response. Conclusion Given the favorable outcome with timely initiation of corticosteroid therapy, COP should be entertained in patients presenting with a diffuse micronodular pattern on CT imaging. This abstract is funded by: none