Histopathology of VGKC Antibody–associated Limbic Encephalitis

We describe histopathology from whole brain in a patient with autoimmune limbic encephalitis with high titers of voltage-gated potassium channels (VGKC) antibodies. ### Case report. A 56-year-old man had a 4-month history of intermittent confusion and two seizures. He appeared well but had periods of confabulation and fear. His history included borderline hypertension. He had stopped smoking. Blood pressure was 147/102 mm Hg. Mini-Mental State Examination score1 was 18/30, indicating disorientation with poor working memory. The patient's VGKC-Ab level was 3,327 pM (normal, 0–100).2 His Na level was 130 mmol/L (normal, 135–145 mmol/L). Antineuronal (anti-Hu and Yo) and thyroid antimicrosomal antibodies, erythrocyte sedimentation rate, C-reactive protein, dsDNA, extractable nuclear antigen, antineutrophil cytoplasmic antibodies, B12, folate, angiotensin-converting enzyme, chest x-ray, and treponemal serology were normal. The patient refused a lumbar puncture. The EEG showed sharp waves over both frontoparietal regions. Brain MRI (T2 and fluid-attenuated inversion recovery) showed left hippocampal atrophy. The patient died in his sleep 7 days after the laboratory studies began. The patient's brain weighed 1,367 g and was macroscopically normal. Paraffin-embedded specimens (4–7 μm thickness) were stained with hematoxylin & eosin (Nissl methods). Immunohistochemistry was performed using antibodies against CD3, CD4, CD8, CD20, CD45, CD68, glial fibrillary acid protein, herpes simplex virus types 1 and 2, measles, cytomegalovirus, SV40, and toxoplasma. Staining for infectious agents was negative. There were no organisms, …