It is strongly advised to check for AQP4 antibodies in SLE patients who develop a severe, uni-, or bilateral subacute loss of vision with pain and a limited steroid response in the acute phase, as AQP4-IgG seropositivity is common in patients with SLE who present with NMOSD, longitudinally extensive transverse myelitis, or ON [50]. This evidence concerns the gene AQP4 and systemic lupus erythematosus.