Aquaporin-4-IgG positive neuromyelitis optica spectrum disorder in a paraneoplastic context

The association between aquaporin-4-immunoglobulin-G-positive neuromyelitis optica spectrum disorder (AQP4-IgG-NMOSD) and cancer via a plausible immunological response has been reported. Here, we investigated the frequency of cancer in a large cohort of patients with AQP4-IgG-NMOSD.Between May 2005 and January 2023, patients with AQP4-IgG-NMOSD and a history of cancer were included by searching for diagnostic codes of both NMOSD and cancer in the electronic medical records and/or reviewing the database of the National Cancer Center registry of inflammatory diseases of the central nervous system. Probable paraneoplastic AQP4-IgG-NMOSD was defined according to the 2021 Criteria for Paraneoplastic Neurological Syndrome.Of 371 patients with AQP4-IgG-NMOSD, 23 (6.2%) had a history of cancer and four (1.1%) experienced NMOSD in a paraneoplastic context. Among the four patients with probable paraneoplastic AQP4-IgG-NMOSD, the types of cancer were lung (1 adenocarcinoma, 1 squamous cell carcinoma) and colorectal (2 adenocarcinomas). In three patients, the first NMOSD symptoms developed after a cancer diagnosis (median, 8 months [range, 4-23]), and one patient's symptoms preceded the cancer diagnosis (6 months). Compared to the 367 non-paraneoplastic patients, those in the paraneoplastic context had an older age at onset (median: 59.5 vs. 37 years, p = 0.012) and a higher proportion of longitudinally extensive transverse myelitis (LETM) as an initial manifestation (4/4[100%] vs. 130/367[35.4%], p = 0.017).In a large cohort of patients with AQP4-IgG-NMOSD, the frequency of cancer was low. Older age, LETM features at onset, and adenocarcinoma as the histological type were usually observed in patients with AQP4-IgG-NMOSD in a paraneoplastic context.