A new study suggests that organizing pneumonia (OP) might represent a pulmonary manifestation of anti-AQP4 antibody-positive neuromyelitis optica spectrum disorder (NMOSD).

The study, published in Respiratory Investigation, concludes that the anti-AQP4 antibody may cause complement-dependent lung epithelial cell cytotoxicity, a possible underlying mechanism in OP development.

“This study conducted a retrospective review of anti-AQP4 antibody-positive NMOSD patients to clarify the clinical manifestations in terms of pulmonary involvement,” the authors wrote. “We further performed immunohistochemical evaluations on the lung biopsy specimens of the involved lungs of patients with anti-AQP4 antibody-positive NMOSD.”

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The research team conducted a retrospective review of 52 anti-AQP4 antibody-positive patients with NMOSD at a single center in Japan. Four patients were found to have pulmonary involvement, and via high-resolution CT, typical features of OP were observed in all four.

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Most of the OP lesions in the patients had developed simultaneously with the symptoms of NMOSD. The patients were all treated with corticosteroids with subsequent significant clinical and radiological improvements after 6 months of therapy.

Given that 75% of the patients with OP were male, the authors suspect male predominance in this disease. Furthermore, the coincidence of pulmonary involvement with NMOSD symptom evolution supports the hypothesis that OP is a pulmonary manifestation of NMOSD.

The authors caution that chest radiography has limited sensitivity for OP, so its frequency could have been underestimated. However, CT was able to confirm that 75% of the patient cohort did not have pulmonary involvement, suggesting that it is sensitive enough to be a first-line screening test in these patients. The authors recommend careful consideration of the patient history in addition to chest CT to evaluate the possibility of OP.


Furube A, Katoda T, Gochi M, et al. Clinical features of organizing pneumonia in anti-aquaporin-4 antibody-positive neuromyelitis optica spectrum disorders. Respir Investig. Published online July 20, 2022. doi:10.1016/j.resinv.2022.06.008