Human T cell leukemia virus type 1 or HTLV-1 infection is a public health problem in endemic regions like Japan, Central America or Africa. Although the majority of HTLV-1 carriers remain asymptomatic throughout their lives, some patients could develop neurological disorder, inflammatory arthropathy also called HTLV-1-associated arthropathy or T-cell malignancy, the adult T-cell leukemia/lymphoma or ATL with a very poor prognosis. Described to be very close to rheumatoid arthritis, HTLV-1-associated arthropathy patients have few or no response to the first line therapy with corticosteroids and disease modifying antirheumatic drugs or DMARDs. The use of anti-TNF-α agents in these patients is an interesting alternative but asks the question of risk of developing an adult T-Cell leukemia/lymphoma. We reported an exceptional case of a smoldering ATL patient with an HTLV-1-associated arthropathy, refractory to corticosteroid, DMARDs and rituximab therapy, treated successfully with etanercept, without progression to aggressive ATL after 5 years.