Limbic Encephalitis With Dual Positivity

Limbic encephalitis is a well-defined clinical disorder among paraneoplastic neurological syndromes. Although it is not always possible to identify specific autoantibodies in limbic encephalitis, the presence of anti-neuronal nuclear antibody type 1 (ANNA1 or anti-Hu), anti-Ma2, collapsin response mediator protein 5 (CRMP-5-IgG or anti-CV2), anti-GABA receptors and anti-amphiphysin antibodies are often detected. A 66-year-old male patient with complaints of forgetfulness was evaluated in our clinic after having seizures. In the neurological examination, the patient was found to be confused. In cranial MR fluid-attenuated inversion recovery (FLAIR) and T2-weighted images, the right hippocampal and parahippocampal structures showed hyperintense areas complying with limbic encephalitis. He had improvement with a course of 2 g/kg intravenous immunoglobulin (IVIG) followed by high-dose methylprednisolone therapy. Following the high-dose methylprednisolone therapy, anti-PCA1 (Yo) and anti-amphiphysin antibodies were positive and the tissue pathology report confirmed combined small-cell carcinoma and large-cell neuroendocrine carcinoma of the lung. In recent years, paraneoplastic neurological syndromes are better recognized with the identification of specific antibodies and the ubiquitous information on pathogenesis. This is the first known report in the literature that a case with both positive anti-PCA1 (Yo) and anti-amphiphysin antibodies together and underlying small-cell and large-cell neuroendocrine carcinomas.