De Mendoza, CarmenPirón, MariaGonzalez, RocíoJiménez, AnaCaballero, EstrellaRoc, LourdesBenito, RafaelRamos, Jose ManuelSoriano, VicenteHTLV Spanish Study Group2025-01-072025-01-072019-01-162328-8957https://hdl.handle.net/10668/24876Although only 8%-10% of persons infected with human T-cell leukemia virus type 1 (HTLV-1) may develop virus-associated diseases lifelong, misdiagnosis of asymptomatic infected carriers frequently leads to late diagnoses. A nationwide HTLV-1 register was created in Spain in 1989. A total of 351 infected persons had been reported by the end of 2017. We examined all new HTLV-1 diagnoses during the last decade and compared their clinical presentation. A total of 247 individuals with HTLV-1 infection had been reported in Spain since year 2008. The incidence has remained stable with 20-25 new diagnoses yearly. Women represented 62%. Only 12% were native Spaniards, most of whom were foreigners from Latin America (72.5%). Up to 57 (23%) individuals presented clinically with HTLV-1-associated conditions, including subacute myelopathy (n = 24; 42.1%), T-cell lymphoma (n = 19; 33.3%), or Strongyloides stercoralis infestation (n = 8; 14%). Human T-cell leukemia virus type 1 diagnosis had been made either at blood banks (n = 109; 44%) or at clinics (n = 138; 56%). It is interesting to note that Spaniards and especially Africans were overrepresented among patients presenting with HTLV-1-associated illnesses, suggesting that misdiagnosis and late presentation are more frequent in these populations compared to Latin Americans. Given that 23% of new HTLV-1 diagnoses in Spain are symptomatic, underdiagnosis must be common. Although screening in blood banks mostly identifies asymptomatic Latin American carriers, a disproportionately high number of Spaniards and Africans are unveiled too late, that is, they already suffer from classic HTLV-1 illnesses.enAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-nd/4.0/HTLV-1adult T-cell leukemiaepidemiologymyelopathyscreeningresearch article30815504open access10.1093/ofid/ofz036PMC6386801https://academic.oup.com/ofid/article-pdf/6/2/ofz036/27975432/ofz036.pdfhttps://pmc.ncbi.nlm.nih.gov/articles/PMC6386801/pdf