Human T-lymphotropic virus type 1 (HTLV-1) infections are associated with varying degrees of HTLV-1 viral load and spasticity. Increased viral load is associated with higher risk of developing HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The authors performed a cross-sectional study of 24 people with HAM/TSP in Lima, Perú, to determine if higher HTLV-1 viral load was correlated with increased muscle tone, measured with a device providing quantitative spasticity assessment (QSA). Median HTLV-1 viral load was 17.0 copies/100 peripheral blood mononuclear cells and QSA value was 39.9 Newton-meters/radian. HTLV-1 viral load was significantly correlated with QSA value (Spearman rho = .48, P = .02), suggesting viral load may play a role in expression of symptomatic neurologic disease. Longitudinal studies are needed to determine if treatments that reduce viral load will reduce muscle tone.
Zunt, J. R., Montano, S. M., Beck, I., Alarcón, J. O. V., Frenkel, L. M., Bautista, C. T., Price, R., & Longstreth, W. T. (2006). Human T-lymphotropic virus type 1-associated myelopathy/tropical spastic paraparesis: Viral load and muscle tone are correlated. Journal of NeuroVirology, 466-471. https://doi.org/10.1080/13550280601039642