Abstract

A patient presented to the Walton Centre for Neurology and Neurosurgery (WCNN) with non-specific fatigue. A voltage gated potassium channel (VGKC) antibody assay was requested, among other investigations. A titre of 0.151 (normal range: 0–0.1 nmol/l) was detected and subsequent CT) of chest showed a thymoma. This led us to ask the following question: What is the clinical spectrum and incidence of malignancy in positive VGKC antibody patients? We performed a retrospective analysis of patients with positive VGKC antibodies from WCNN between 2001 and 2009 (n=52). Limbic Encephalitis (LE) was seen in 20% (n=10), and Peripheral Nerve Hyperexcitibility (PNH) in 33% (n=17). No cases of Morvan's syndrome were identified. Other associations included Guillain–Barre Syndrome, Chronic Inflammatory Demyelinating Polyneuropathy, Non-Epileptic Attack Disorder, Relapsing Remitting Multiple Sclerosis (RRMS), Primary Lateral Sclerosis, Chronic Regional Pain Syndrome, and an akinetic rigid syndrome. Titres >0.4 nmol/l were detected in 15 patients; PNH (n=5), LE (n=9), RRMS (n=1). Overall five malignancies were detected (10%); thymoma (n=2), small cell carcinoma lung (n=1), astrocytoma (n=1), and prostatic adenocarcinoma (n=1). The clinical spectrum is intriguing, but raises the question of whether testing was appropriate in all cases. This study highlights the importance of correlating clinical context with VGKC antibody testing.