Of the six patients with spurious intrathecal Ig synthesis, one patient with autoimmune encephalitis and IgG as well as IgA synthesis had persistence of an increased IgA fraction in the further course, whereas the other five (two with autoimmune encephalitis, two with neuromyelitis optica, and one with myelitis) had a CSF analysis before PE without increased intrathecal immunoglobulin fractions. This evidence concerns the gene CD79A and neuromyelitis optica.