Potassium channel antibodies in two patients with reversible limbic encephalitis

Limbic encephalitis (LE) is often associated with lung, thymic, or testicul ar tumours and antibodies to Hu, CV2, or Ma2 (Ta) antigens. In these cases, it generally has a poor prognosis. Here we describe two patients with symp toms of LE, negative for typical paraneoplastic antibodies, in whom antibod ies to voltage-gated potassium channels (VGKC) were detected retrospectivel y in serial serum samples. Patient 1 had a thymoma recurrence, but in patie nt 2 no tumour has been detected in the years following presentation. Plasm a exchange was effective in reducing VGKC antibody levels, with substantial improvement in mental symptoms in patient 1. In patient 2, the VGKC antibo dies fell spontaneously over two years, with almost complete recovery of me ntal function. Although neither patient had obvious neuromyotonia at presen tation, both showed excessive secretions. We suggest that patients with lim bic symptoms and excessive secretions should be tested for VGKC antibodies, and, if they are present, prompt and effective immunosuppressive treatment should be considered.