(Devic’s disease) a condition that resembles multiple sclerosis. The diagnosis is confirmed by the finding of the antiaquaparin-4 antibody (NMO IgG antibody). Typically there is a transverse *myelitis, producing paralysis and numbness of the legs and trunk below the inflamed spinal cord, and *retrobulbar (optic) neuritis affecting both optic nerves. The attacks of myelitis and optic neuritis may coincide or they may be separated by days or weeks. Recovery from the initial attack is often incomplete and severe relapses occur commonly unless treatment with immunosuppressive therapies is started.