Higher vitamin D levels, particularly before the age of 20, have been associated with a lower risk of developing MS later in life,113 with additional evidence from the EnvIMS study, where supplementation and sun exposure support its protective effect.111,114 Recently, high vitamin D levels have also been shown to correlate with decreased axonal damage, as assessed by CSF NfL levels in patients with MS.115. Here, NEFL is linked to myeloid sarcoma.