CHIT1 and tropical spastic paraparesis: HAM/TSP patients also displayed increased CHIT1 CSF levels (1.74 ng/mL IQR, 0.97-3.32 ng/mL) compared to the HTLV-1 AC (0.62 ng/mL, IQR 0.45-0.79 ng/mL) and control groups (0.73 ng/mL, IQR 0.36-1.21 ng/mL) (Dunn’s posthoc test p = 0.006 and 0.017, respectively) (Figures 2A, B).