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

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