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PLoS Negl Trop Dis. 2019 May 1;13(5):e0006967. doi: 10.1371/journal.pntd.0006967. eCollection 2019 May.

Detection of clinical and neurological signs in apparently asymptomatic HTLV-1 infected carriers: Association with high proviral load.

Author information

Institute of Infectious Diseases "Emilio Ribas" (IIER) of São Paulo, São Paulo, SP, Brazil.
Laboratory of Dermatology and Immunodeficiencies, Department of Dermatology, University of São Paulo Medical School, Brazil.
Institute of Tropical Medicine of São Paulo, São Paulo, SP, Brazil.
Department of Preventive Medicine, University of São Paulo Medical School, São Paulo, Brazil.


Several studies suggest that HTLV-1 infection may be associated with a wider spectrum of neurologic manifestations that do not meet diagnostic criteria for HAM/TSP. These conditions may later progress to HAM/TSP or constitute an intermediate clinical form, between asymptomatic HTLV-1 carriers and those with full myelopathy. Our aim was to determine the prevalence of HTLV-1-associated disease in subjects without HAM/TSP, and the relationship between these findings with HTLV-1 proviral load (PVL).


175 HTLV-1-infected subjects were submitted to a careful neurological evaluation, during their regular follow up at the HTLV outpatient clinic of the Institute of Infectious Diseases "Emilio Ribas", São Paulo city, Brazil. Clinical evaluation and blinded standardized neurological screening were performed for all the subjects by the same neurologist (MH).


After the neurological evaluation, 133 patients were classified as asymptomatic and 42 fulfilled the criteria for intermediate syndrome (IS). The mean age of the enrolled subjects was 46.3 years and 130 (74.3%) were females. Clinical classification shows that neurological symptoms (p<0.001), visual disorders (p = 0.001), oral conditions (p = 0.001), skin lesions (p<0.001), bladder disorders (p<0.001), and rheumatological symptoms (p = 0.001), were strongly associated to IS, except for disautonomy (p = 0.21). A multivariate analysis revealed that HTLV-1 proviral load, oral conditions, bladder disorders and rheumatological symptoms were independently associated with the IS.


We found some early alterations in 42 patients (24%), particularly the presence of previously not acknowledged clinical and neurological symptoms, among subjects previously classified as "asymptomatic", who we reclassified as having an intermediate syndrome.

Conflict of interest statement

No. The authors have declared that no competing interests exist.

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