Magnetic resonance imaging of the brain showed extensive white matter changes with enhancement along the arachnoid surface in the interhemispheric fissure extending over the frontal lobes bilaterally without any evidence of acute infarct in diffusion-weighted imaging sequence or any vascular abnormality on magnetic resonance angiography (Figure). Her erythrocyte sedimentation rate and C-reactive protein level were elevated. A high titer of cyclic citrullinated peptide antibody confirmed RA. Cerebrospinal fluid (CSF) analysis showed a white blood cell count of 12/µL (to convert to ×109 per liter, multiply by 0.001), red blood cell count of 1/µL, protein level of 0.055 g/dL (to convert to grams per liter, multiply by 10), glucose level of 58 mg/dL, and 4 oligoclonal bands corresponding to serum sample. Results from infectious disease workups, including rapid plasma reagin, QuantiFERON (Qiagen), and human immunodeficiency virus, were negative. Chest computed tomography did not reveal any pathology or pulmonary nodules. Cerebrospinal fluid angiotensin-converting enzyme level was not elevated. Extensive workup was done to rule out coexisting immunological disorders, especially antiphospholipid syndrome. Lupus anticoagulant test results for partial thromboplastin time–lupus anticoagulant (PTT-LA) was 36 seconds and for dilute Russell viper venom test (DRVVT) was 27 seconds. Both were within normal range. Anticardiolipin IgG, IgA, and IgM levels were 8 IgG, 2 IgA, and 5 IgM phospholipid units, respectively, where values less than 23 IgG, less than 22 IgA, and less than 11 IgM phospholipid units, respectively, are considered negative. Anti–β-2-glycoprotein IgG, IgA, and IgM levels were 1, 7, and 8 U (<20 U is normal). These results eliminated antiphospholipid syndrome. Antineutrophil cytoplasmic antibody test results were negative (Table).