Patient 2 was AQP4-IgG positive in both serum and CSF, and despite acute treatment, experienced a fatal relapse 6 months later with longitudinally extensive transverse myelitis while on low-dose prednisone monotherapy.<h4>Conclusions</h4>Isolated APS may represent an important yet under-recognized manifestation of post-COVID-19 autoimmune neuroinflammation. Here, AQP4 is linked to autoimmune polyendocrinopathy.