A case of anti-Hu antibody- and anti-GluRε2 antibody-positive paraneoplastic neurological syndrome presenting with limbic encephalitis and peripheral neuropathy

We report a case of paraneoplastic neurological syndrome with anti-neuronal antibodies, namely anti-Hu and anti-GluRε2 antibodies in sera. A 72-year-old male had a transient history of eye movement disorder and sensory neuropathy, which improved spontaneously. Two years later, he was admitted to another hospital because of gait disturbance, numbness of the hands and an attack of unconsciousness with generalized convulsion. He was admitted to our hospital with prolonged consciousness disturbance and muscular weakness of all extremities. On admission his consciousness deteriorated slightly without neck stiffness. His cranial nervous system was normal except for incomplete abduction and elevation of both eyes. The patient had severe distal dominant weakness and atrophy in the muscles of all four limbs. Muscle tonus was decreased and hyporeflexia was noted in the four extremities. Plantar response was extensor. Neither sensory disturbance nor ataxia was observed. Cranial MRI showed T ₂-weighted high intensity lesions in the bilateral mesial temporal lobes, including the hippocampi. A nerve conduction study revealed motor-dominant peripheral neuropathy with prolonged latency; the amplitudes of compound muscle action potentials were severely reduced in all four limbs and those of sensory nerve action potentials were moderately reduced in the right upper and lower extremities. We also found a left hilar lymphadenopathy showing accumulation of FDG on PET, suggesting a possibility of malignancy. Anti-Hu and anti-GluRε2 antibodies were detected in sera but not in CSF. We diagnosed him with limbic encephalitis and peripheral neuropathy due to paraneoplastic neurological syndrome and treated him with two courses of intravenous immunoglobulin (IVIg) (400 mg/kg, 5 days). The consciousness disturbance, and prolonged distal latency revealed by motor nerve conduction studies improved slightly. Although the roles of anti-neuronal antibodies in paraneoplastic conditions remain unknown, we consider that IVIg may be worth using to treat cases with anti-Hu and anti-GluRε2 antibodies.