Neurofilament light chain (NFL) in CSF correlates with long-term prognosis in MS [9], is a risk factor for conversion from clinically isolated syndrome (CIS) to relapsing remitting multiple sclerosis (RRMS) [10], and decreases on treatment with fingolimod and natalizumab [11, 12]. The gene discussed is NEFL; the disease is myeloid sarcoma.