AQP4 and tropical spastic paraparesis: Serum AQP4-Ab were detected in 20 out of 34 (59%) patients in the NMOSD group, which included patients with NMO (positive in 14/17 cases) and patients with syndromes considered to confer a high risk for conversion to NMO (recurrent ON or LETM; positive in 6/17 cases) (see Table 1 for details), but in none of the patients previously diagnosed with HAM/TSP (n = 23), in none of the patients with positive HTLV-1 serostatus but no neurological symptoms at the time of presentation (n = 20), and in none of the HCs (n = 23) (p<0.0001; Chi-square test).