Numerous studies have shown that NfL levels increase during MS relapses and correlate with MRI lesion development (Disanto et al., 2016, 2017; Novakova et al., 2017b; Barro et al., 2018), disease activity, disability and disease progression (Thebault et al., 2020). The gene discussed is NEFL; the disease is myeloid sarcoma.