However, clinicians should pay particular attention in anti-AQP4 negative patients, in patients with a known malignancy or cancer risk factors (e.g. smoking), and/or if clinical presentation is atypical, since paraneoplastic myelitis and/or ON in association with anti-CV2/CRMP5, –Hu or –amphiphysin antibodies might clinically mimic NMOSD [7–10]. Here, AQP4 is linked to cancer.