One month after steroid and IVIG introduction, MMSE had improved to 22/30, disorientation had partially improved, and visual hallucinations had disappeared. and/or pleocytosis and white matter lesions in the absence of vascular risk factors were accepted as atypical features. 2.2. Antibody Assessments Voltage-gated potassium channel (VGKC) complex antibodies (normal value 100?pM) were identified by radioimmunoprecipitation using 125I-dendrotoxin-VGKC . Antiglutamic acid decarboxylase (GAD) antibody (normal value 10?U/mL) was investigated by commercial ELISA packages (Euroimmun, Luebeck, Germany) using standard protocols. The antibodies to N-methyl-D-aspartate receptor (NMDAR), = 39)= 10)= 1) /th /thead Presenile onset of dementia1 (2.5%)2 (20%)0 (0%)Rapid progression5 (12.8%)3 (30%)1 (100%)Subacute onset of dementia0 (0%)0 (0%)1 (100%) Atypical onset of dementia (PPA or PCA)1 (2.5%) 1 (10%)0 (0%)Seizures6 (15.3%) 3 Sulpiride (30%) 0 (0%) Positive OCB and/or CSF pleocytosis*1 (2.5%)2 Sulpiride (20%)0 (0%) Multiple white matter lesions Sulpiride without a vascular risk factor1 (2.5%)1 (10%)0 (0%) Open in a separate window AD: Alzheimer disease; FTD: frontotemporal dementia; DLB: dementia with Lewy body; PPA: main progressive aphasia; PCA: posterior cortical atrophy; OCB: oligoclonal band; CSF: cerebrospinal fluid. *CSF examination was performed only in 7 dementia patients. The NMDAR antibody was positive in one patient fulfilling the DLB criteria (Case 1). Another individual with bipolar disease (Case 2) experienced low (35.4?U/mL) GAD antibody levels. No antibodies were detected in sera of other cases. em Case 1 /em . This 58-year-old man presented with a 4-month history of amnesia, aggressive behavior, visual hallucinations, urinary incontinence, and clinically diagnosed rapid vision movement (REM) behavior disorder (RBD) fluctuating from hour to hour. His wife reported acting out violent dreams, vocalization, and episodes of kicking, biting, and screaming during sleep consistent with RBD occurring every 1 or 2 2 occasions every night. A polysomnogram could not be performed. Neurological examination revealed disorientation in time and place, positive glabellar tap, rigidity, and bradykinesia. The patient demonstrated a stooped posture and festinant gait without retropulsion. He did not display tremor and did not have a history of treatment with any medication including antipsychotics. The patient scored 13/30 on MMSE and 4 on GDS. Detailed neuropsychological examination showed moderately impaired attention, verbal memory, visual memory, and visual-spatial belief. Routine blood assessments and T1-, T2-, FLAIR-, and diffusion-weighted MRIs were normal. EEG showed widespread slow waves. CSF cell count, protein concentration, and 14-3-3 protein levels were normal and no OCB were detected. Serum COL4A1 NMDAR antibody was found positive, whereas other investigated antibodies were unfavorable. The atypical features included subacute onset of dementia and quick progression (Table 1). His symptoms promptly regressed under pulse steroid (1000?mg/day iv for 5 days) and intravenous immunoglobulin (IVIG) (30?gr total for 5 days) treatments. One month after steroid and IVIG introduction, MMSE experienced improved to 22/30, disorientation experienced partially improved, and visual hallucinations experienced disappeared. He subsequently received monthly pulse steroid and IVIG treatments and his symptoms completely disappeared in 3 months. em Case 2 /em . The GAD-antibody positive bipolar disease individual was a 31-year-old woman with disease duration of 3 years. She experienced common manic and depressive episodes lasting from a few days to weeks with no psychotic features. During blood sampling for antibody screening, she experienced moderate depressive symptoms under treatment. Her medical history did not suggest subacute onset or quick progression and her MRI, EEG, and neuropsychological examinations were normal. 4. Conversation The key obtaining of our study was the clinical presentation of NMDAR antibody-associated autoimmune encephalitis masquerading as DLB, demonstrating the potential for misdiagnosis of a reversible condition as a progressive dementia syndrome. Cognitive impairment has been reported in association with several autoantibodies directed against neuronal antigens such as VGKC-complex [1, 2], NMDAR [3, 9], and GAD [10, 11]. Anti-NMDAR encephalitis is particularly associated with psychiatric and neurological symptoms such as memory problems, seizures, hallucinations, and.