A Case of Late-Onset Neuromyelitis Optica Spectrum Disorder Associated With Cryptogenic Organizing Pneumonia.

Introduction: Systemic diseases can be found in neuromyelitis optica spectrum disorder (NMOSD) as a co-existing disease with paraneoplastic syndrome, sarcoidosis, or connective tissue disease. Cryptogenic organizing pneumonia (COP) in NMOSD with no evidence of these systemic disorders has rarely been reported. Case presentation: We present a 75-year-old patient who showed multifocal longitudinally extensive transverse myelitis and bilateral lung lesions that was seropositive for aquaporin-4 (AQP4) antibody. The patient initially presented with chronic cough, myalgia, and severe bilateral truncal neuropathic pain, and initial chest computed tomography demonstrated multifocal consolidations with reversed halo sign involving both lobes. Since this patient was over 50 years of age, our differential diagnoses included lung cancer and sarcoidosis. Through extensive studies including lung biopsy, an idiopathic type of diffuse interstitial lung disease-cryptogenic organizing pneumonia (COP)-was finally diagnosed. The patient was treated with high-dose methylprednisolone and it was tapered with oral steroids; mycophenolate mofetil was later added to the regimen. After treatment, the severe neuropathic pain and multifocal lung consolidation resolved. Conclusion: Herein, we presented a case of late-onset NMO with nonneoplastic, nonsarcoidosis, diffuse interstitial lung lesions, which is the finding of COP.