Spontaneous remission of the micronodular pattern in cryptogenic organizing pneumonia

Organizing pneumonia (OP) is a common interstitial lung disease, pathologically characterized by polypoid granulation tissue in the alveolar ducts and alveoli. In clinical practice, OP occasionally presents as non‐resolving pneumonia. The typical radiographic pattern of OP is characterized by dense consolidation with ground‐glass opacities. Diffuse micronodular pattern of OP (MNOP) is a rare radiographic manifestation that mimics non‐resolving bronchiolar diseases such as pulmonary tuberculosis or hypersensitivity pneumonitis. Steroid therapy is usually effective for MNOP; however, spontaneous remission in MNOP has never been reported. Herein, we report a case of a diffuse micronodular form of cryptogenic OP (COP) that was diagnosed via transbronchial biopsy (TBB) and resolved spontaneously within a few months. Our case highlights that MNOP may resolve spontaneously similar to other forms of OP, and mild cases may be under‐recognized. Furthermore, careful observation could be an option for managing MNOP with mild and non‐progressive symptoms.