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.