IFNB1 and myeloid sarcoma: Our observations introduce the novel concept that the differential treatment response to IFNβ is not explained by a specific set of IRGs, but rather by a generally augmented IRG response to IFNβ injections, and that response to IFNβ injection unmasks a subset of patients who not only respond poorly to IFNβ treatment, but who have a pathogenetically distinct form of MS.