Widespread active inflammatory lesions in a case of HTLV-I-associated myelopathy lasting 29 years

An autopsy case of human T-lymphotropic virus type I (HTLV-I)-associated myelopathy (HAM) of 29 years' duration is reported. The patient had no history of surgery or blood transfusion and likely contracted HTLV-I sexually while traveling in an endemic area. At age 45, the patient began to experience gait disturbance; he later developed spastic tetraparesis. Autopsy revealed marked gross spinal cord atrophy, particularly in the middle to lower thoracic levels. Myelin and axonal degeneration were identified predominantly in the middle to lower thoracic spinal cord, extending into the medulla oblongata and lumbar cord. Inflammatory infiltrates of mononuclear cells were diffuse in the white and gray matter of the spinal cord and medulla oblongata, particularly in perivascular areas. These infiltrates were also observed in perivascular areas of the pons, midbrain, cerebellum, and cerebrum. More than half of the infiltrating cells were positive for the pan-T cell marker UCHL-1, but some were positive for the B cell marker SL-26. There were far more CD8-positive cells than CD4-positive cells in the spinal parenchyma and perivascular areas. Neurons in the anterior horn, Clarke's column, and intermediolateral column were relatively well preserved. Active chronic inflammation was indicated. Despite the 29-year history of HAM, the presence of an active inflammatory reaction is surprising. We discuss possible modulation of the histopathological manifestations of HAM by corticosteroid therapy.