Demyelination observed in RA patients receiving anti-tumor necrosis factor alpha treatment could be attributed to the unmasking of latent preexisting multiple sclerosis (MS), the emergence of a new demyelinating event (either MS or MS-like), or to the incidental coexistence of the two disorders.(31) Nevertheless, morbidity and mortality rates remain high, despite aggressive treatment with cyclophosphamide or biologic agents. The gene discussed is TNF; the disease is myeloid sarcoma.