Unmasking HAM/TSP: understanding HTLV-1-driven neurological disease

Human T-cell Lymphotropic virus type 1 (HTLV-1) is a retrovirus that infected 10-20 million of individuals worldwide. HTLV-1 infection is associated with the development of various diseases, including HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and adult T-cell leukemia/lymphoma (ATLL). HAM/TSP is a chronic progressive neuroinflammatory disease characterized by motor impairment, spasticity, and other neurological manifestations. This narrative review provides a comprehensive overview of HAM/TSP following HTLV-1 infection. We discussed the virology and epidemiology of HTLV-1, transmission modes, and risk factors for infection. Furthermore, we delved into the pathogenesis of HAM/TSP disease, exploring the role of neuroimmunology and immune dysregulation. Viral proteins and host genetic factors that influence disease progression are also examined. Diagnostic approaches, including laboratory tests and imaging techniques, are discussed, along with available treatment options and immunomodulatory therapies. Additionally, we highlighted the history of HAM/TSP disease and provide insights into the global distribution and epidemiology. Finally, the current status and challenges of HTLV-1 vaccine development are addressed. This narrative review aims to enhance understanding of HAM/TSP disease following HTLV-1 infection, shedding light on key aspects of their etiology, diagnosis, and management, while emphasizing the need for continued research and public health interventions.