Human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP): recent perspectives.

Human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a well-defined clinicopathological entity, and approximately 1,900 patients with HAM/TSP have been reported in the world. Improved polymerase chain reaction (PCR)-based in situ techniques have allowed a better appreciation of the cellular localization of the virus activation in infected patients, and there is accumulating evidence that HAM/TSP is characterized by a distributional bias of viral activation between the blood flow and central nervous system (CNS). This review summarizes the current status of our understanding of HAM/TSP, and emphasizes the possible pathogenic involvement of cellular interactions between infected cells and responding immunocompetent cells in the CNS of patients with HAM/TSP. In addition, the notable systemic manifestations with or without myelopathy in HTLV-I-infected individuals are described.