Neuropathology of HTLV-I-associated myelopathy--a report of two autopsy cases.

A neuropathological analysis was performed in two autopsy cases of HTLV-I-associated myelopathy. The thoracic spinal cords were most severely affected and the histopathological findings consisted of mononuclear cell infiltration, marked destruction of myelin and axons and astrocytic gliosis. More than half the infiltrated cells were positive for pan-T cell marker; B cells were sparse in the parenchyma and subarachnoid spaces. CD4 and CD8 positive cells were found in the early stages of the lesions. CD8, however, predominated over CD4 in the other stages. It appeared that a chronic inflammatory process had started at the middle to lower thoracic cord and had extended gradually in both directions. The middle thoracic spinal cord is known to have the poorest blood supply, and the horizontal distribution of inflammatory cells at this region correlated with the most distal supply of the anterior spinal artery.