A 62-year-old man presented to the Emergency Department of Sant'Orsola-Malpighi University Hospital in Bologna, Italy, because of a rapidly progressive cognitive decline. He had recently come back to Italy after a 3-month journey in Brazil because relatives found him confused while speaking over the phone. Because of global slowing, disorientation, and confabulation, which developed over the previous 2 months, he underwent a brain MRI in Brazil, which showed cortical atrophy and multiple white matter lesions with no contrast enhancement. No further clinical information about the medical assessment in Brazil was available.Since age 34 years, the patient was on highly active antiretroviral therapy (ART) (abacavir 600 mg/d, lamivudine 300 mg/d, darunavir 800 mg/d, and ritonavir 100 mg/d) for HIV infection with good adherence. His medical history was also relevant for hypertension, diabetes, squamous cell carcinoma of the anus, psoriatic arthritis, including skin psoriasis, dactylitis, nail dystrophy, a negative rheumatoid factor, and diffuse proliferative lupus-like glomerulonephritis.At the first medical evaluation, the patient was drowsy, spatially and temporally disoriented, with reduced verbal fluency, miotic reagent pupils, and a mask face. He also had axial and limb plastic hypertonia and dystonia of both hands. Arterial pressure was 130/ 80 mm Hg, heart rate was 90/min, and arterial blood gas test was within the normal range. A cerebral CT scan was also unremarkable. Blood examinations, including a toxicology screen, were normal, except for mean corpuscular volume 105 fL, mean corpuscular hemoglobin 38 pg, aspartate aminotransferase 80 U/L, lactate dehydrogenase 331 U/L, and C-reactive protein 1.65 mg/dL. The patient underwent a lumbar puncture to rule out infectious diseases.CSF analyses revealed proteins 93 mg/dL, glucose 70 mg/dL, leukocytes 1/mmc, immunoglobulin G 11.8 mg/dL, albumin 69.1 mg/dL; the albumin CSF/serum ratio was 20.8, indicative for abnormal permeability of the blood-CSF barrier. Blood testing for autoimmune diseases was negative except for antinuclear antibody 1:80. Plasma CD4 count was 275/mmc (25%). EEG examination documented asymmetric and pseudo-periodic slow spike discharges with maximum amplitude in the right temporal region ( figure 1A).A thorough anamnesis with the relatives revealed a recent relapse of psoriatic arthritis, treated with methylprednisolone, hydroxychloroquine, and methotrexate.