Here, we monitored the longitudinal changes in serum neurofilament light chain (sNfL) levels as a measure of neuro‐axonal injury in CIS patients treated with an 8‐week course of UVB‐PT and correlated NfL levels with magnetic resonance imaging (MRI) lesion volumes (LV) and the risk of conversion to MS. The gene discussed is NEFL; the disease is myeloid sarcoma.