HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP): A comparative study to identify factors that influence disease progression

•Advanced age at disease onset is a significant determinant in rapidly progressing HAM/TSP.•Commonly seen initial symptoms include gait, urinary, and sensory disturbances.•No difference in initial symptoms between the sexes.•CSF pleocytosis, protein and HTLV-1 antibody are useful biomarkers when evaluating disease phenotypes.

ObjectiveHTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) can progress slowly or rapidly even though a set of symptoms such as spastic paraparesis with pathological reflexes and sweating loss of the lower extremities are commonly observed in patients. Although most of the patients are thought to be infected to HTLV-1 from their mothers by breast feeding, symptoms of HAM/TSP typically manifest in patients later in life (50-60 years old in age) and also with a higher prevalence of women to men at a ratio of approximately 3:1. Probability of developing HAM/TSP and how fast an individual's disease may progress from the time of diagnosis could be multifactorial.MethodsWe reviewed the records of 150 patients with HAM/TSP admitted to Kagoshima University Hospital between 2002 and 2014. Laboratory data of cerebrospinal fluid and serum and the clinical measurements including age, age of disease onset, progression rate, duration of illness, initial symptoms, Osame's Motor Disability Score were evaluated. Rapid disease progression of the disease was defined by deterioration of motor disability by > 3 grades within 2 years.ResultsOf 150 HAM/TSP patients in our cohort, 114 cases (76%) were females. Patients presenting with rapid disease progression are approximately 15 years older at the age of onset than those with a protracted disease course, and have increased number of cell, and elevated levels of protein as well as anti-HTLV-1 antibody titer in the CSF, suggesting a more active inflammatory process. There is no significant difference in the average values of clinical and laboratory parameters between the sexes. Furthermore, there is no apparent correlation between rate of disease progression and gender.ConclusionsOur results suggest that age and virus mediated inflammation are correlated with disease phenotypes while additional factors such as host or HTLV-1 genetics and gender may influence disease susceptibility.