Infection with HTLV-1 is a neglected condition, despite being the second most prevalent human retroviral infection worldwide after HIV-1. Current estimates are of 10 million people living with HTLV-1 globally, with high endemic regions located in Equatorial Africa, Latin America and the Caribbean, northeastern Iran, southwestern Japan and Australia [1,2]. Once acquired, either sexually, vertically or parenterally, HTLV-1 infection is lifelong. Although many HTLV-1-infected individuals are asymptomatic and unaware of their infection, roughly 10% will go to develop clinical manifestations, generally after several decades of silent infection, being the most characteristic HTLV-1-associated myelopathy (HAM) and adult T-cell leukemia/lymphoma (ATLL) [3,4].

HAM was originally reported in Martinique, a French overseas territory in the Caribbean region, in patients with tropical spastic paraparesis, in whom seroreactivity to specific anti-HTLV-1 antibodies was unveiled [5]. HAM is a neuroinflammatory subacute disease of the spinal cord. Patients with HAM typically experience chronic lower back pain with early neuropathic urinary bladder symptoms followed by the development of lower limb spasticity [6,7]. Proximal weakness of the lower limbs, which eventually spreads distally, is common. Acute and subacute presentations, with progression to severe paraplegia within a few months, can occur. Poorer prognostic indicators in patients with HAM include a high HTLV-1 proviral load, female sex, age at onset of 50 years or older, and an early rapid clinical progression [8,9].

Herein, we discuss the main features of patients diagnosed to date with HAM in Spain, a non-endemic country with a relatively high migrant flow from regions in Latin America and Equatorial Africa, where HTLV-1 is endemic.