[A case of glioblastoma misdiagnosed initially due to positive finding of anti-glutamate receptor antibody].

A 53-year-old man was admitted to our hospital after suffering four attacks with loss of consciousness and/or topographic agnosia. Three months after the first attack, the cerebrospinal fluid analysis showed no abnormal findings. IgG-autoantibodies and IgM-autoantibodies against glutamate receptor epsilon2 (GluRepsilon2) were detected in cerebrospinal fluid and serum respectively. At that time, we diagnosed him as having limbic encephalopathy. Brain MRI revealed a high intensity lesion on T2-weighted and FLAIR images in the medial regions of the bilateral temporal lobes and splenium. A diffusion-weighted image revealed high intensity lesions which were also weakly enhanced by Gd-DTPA in the deep white matter beside the posterior horns. The patient then developed numbness in the right hand. The cerebralspinal fluid analysis, four months after the onset of the disease, exhibited slight pleocytosis and elevated protein. IgG-autoantibodies against GluRepsilon2 were detected in the serum. The lesions beside the posterior horns were ring-like enhanced more strongly. Brain biopsy led to a diagnosis of glioblastoma. We suggest that patients with autoantibodies against GluRepsilon2 should be carefully diagnosed with limbic encephalopathy associated with autoimmune mechanisms even if radiological findings are typical of the disease.