Instituto Nacional de Ciência e Tecnologia em Doenças Tropicais (INCT-DT N˚ 573839/2008-5).Human T-cell lymphotropic virus type 1 (HTLV-1)-associated inflammatory diseases are not well understood; however, their clinical manifestations may be influenced by the host genetic background. Methods: We genotyped 298 individuals with HTLV-1 and 380 controls for interleukin-10 (IL10) gene variants—rs3024496, rs1800871, rs1800896—and used logistic regression analysis to determine their association with clinical phenotypes. Results: No association with HTLV-1 infection was observed. However, allele A of rs1800896 (1082bp upstream) was associated with protection against neurological impairment, specifically overactive bladder (OR=0.447, 95% CI 0.28–0.70, p=0.001). Conclusions: Our data suggests that IL10 regulation ameliorates neurological damage in HTLV-1 infections.