Until recent years many polymorphisms had been described as related to the progression of HTLV-1infection including human leucocyte antigen (HLA) genes (52), the immunoregulation-related gene FOXP3 (53), the vascular endothelial growth factor (VEGF) gene (54), Tax-responsive elements (TRE) gene (55), Mannose-binding lectin-associated serine protease 2 (MASP2) gene (56) and others that could be related to the pro-viral load control or development of clinical manifestations including HAM/TSP. Here, MASP2 is linked to tropical spastic paraparesis.