CHIT1 and tropical spastic paraparesis: However, since CSF from HAM/TSP patients can be enriched in inflammatory elements (e.g., CHIT1 [11], CXCL10 and metabolites such as neopterin [16, 25], as well as exosomes [26]), we speculated that it may have an impact on the biology of cells of the CNS and may participate in pathogenesis.