Increased concentrations of inflammatory markers such as neopterin [10], tumor necrosis factor (TNF)-α, interleukin (IL)-6, and interferon (IFN)-γ [11], and increase in HTLV-1 antigen-specific intrathecal antibody synthesis [12] have been observed in the cerebrospinal fluid (CSF) of HAM/TSP patients. Here, IFNG is linked to tropical spastic paraparesis.