Seronegative limbic encephalitis in association with Sjögren's syndrome: a rare case report

Limbic encephalitis is often due to an autoimmune or paraneoplastic disease and is always a diagnostic challenge. We report a 31-year-old lady who presented with fever and proximal weakness to start with and afterwards developed refractory focal onset seizures and worsening cognition despite optimum treatment. Evaluation revealed hypokalemia with a normal anion gap metabolic acidosis. Magnetic resonance imaging (MRI) brain showed features of limbic encephalitis. Cerebrospinal fluid (CSF) showed lymphocytosis and CSF autoimmune, paraneoplastic and viral encephalitis panel were negative. However a blood ANA profile clinched the diagnosis when SS-A and Ro 52 were strongly positive. She was given steroids and subsequently plasma exchange. A labial gland biopsy confirmed the diagnosis of Sjögren syndrome. In cases of autoimmune limbic encephalitis with no identifiable cause, serological screening for rheumatological disorders is recommended. Sjögren syndrome is a rare aetiology for autoimmune limbic encephalitis. A detailed history and a step wise approach is always the key to the right diagnosis.