The comparison between MS subgroups at baseline, however, revealed a significantly higher age in PPMS than in RRMS_U (p = 0.003) and in RRMS_I (p = 0.004), as well as higher NFL levels in PPMS than in BMS (p = 0.004) and RRMS_I (p = 0.002) in post-hoc analysis. Here, NEFL is linked to myeloid sarcoma.