An AQP-4-IgG-Positive Patient with Neuroimaging Findings Suggestive of Multiple Sclerosis

BACKGROUND Multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSDs) are 2 similar but distinct diseases. These diseases were difficult to distinguish from each other until aquaporin-4-IgG (AQP-4-IgG) was discovered. The accurate identification of these 2 diseases is crucial for appropriate drug treatment in clinical practice. Herein, we report a case of AQP-4-IgG seroconversion with magnetic resonance imaging (MRI) findings suggestive of MS. CASE REPORT A 54-year-old woman developed weakness in her right lower extremity that gradually returned to normal 4 years ago. Recently, she was admitted to the hospital for numbness and weakness of both lower limbs and the right upper limb for more than 10 days. The clinical and MRI features of the patient suggested a high susceptibility for misdiagnosis of MS. However, careful observation of the MRI revealed the presence of atypical MS lesions ("red flag" signs), indicating the possibility of other diagnoses in this patient. After further examination, serum AQP-4-IgG was detected, suggesting the potential presence of another disorder, NMOSD, in the patient. CONCLUSIONS Attention should be given to the identification of MS MRI "red flag" signs. Even for patients with a high suspicion of MS, it is necessary to conduct antibody tests for AQP-4-IgG, MOG-IgG and other relevant markers to screen for associated diseases because MS disease-modifying therapy approaches may lead to a deterioration in the state of NMOSD patients. Analyzing this case can help us to further distinguish the differences between these 2 types of diseases, which has important practical clinical value.