Neuromyelitis optica with HTLV-1 infection: different from acute progressive HAM?

Acute variant of human T lymphotropic virus type 1 (HTLV-1)-associated myelopathy (HAM) has been postulated as termed "acute HAM" or "rapidly progressive HAM". However, it remains controversial whether HAM itself could cause such rapid progression. We report a patient with HTLV-1 infection, in whom the diagnosis of neuromyelitis optica (NMO) could be made based on relapsing-remitting course of opticospinal disturbance and positive anti-aquaporin-4 (AQP4) antibody. Careful testing of anti-AQP4 antibody is necessary to establish whether or not acute HAM is a clinical variant of HAM.