Acute transverse myelitis is most commonly due to multiple sclerosis; however, it can occur in patients with vasculitis, systemic lupus erythematosus (SLE), antiphospholipid syndrome, other autoimmune disorders, mycoplasmal infections, Lyme disease, syphilis, tuberculosis (TB), COVID-19, or viral meningoencephalitis or in patients taking amphetamines, IV heroin, or antiparasitic or antifungal medications.