Coexistence of paraneoplastic sensory neuronopathy and Lambert-Eaton myasthenic syndrome in a small cell lung cancer patient.

The present report is on a 72-year-old male patient with combined paraneoplastic sensory neuronopathy (PSN) and Lambert-Eaton myasthenic syndrome (LEMS) with small cell lung cancer. He noticed a painful paresthesia of the legs which advanced over seven days, and both hands became numb and painful. Three months later, he was found to have small cell lung cancer by mediastinoscopic examination. PSN was diagnosed by clinical symptoms and anti-Hu antibody, and LEMS was diagnosed by the waxing phenomenon on an electromyogram (incremental in compound muscle action potential up to 120%) and autoantibody against the presynaptic voltage-gated calcium channel. High titers of anti-Hu antibody were detected in the serum (1:12800) and cerebrospinal fluid (1:320). Although a partial response to chemoradiotherapy was obtained, the neurologic symptoms of PSN did not improve. The anti-Hu antibody titers obtained on five different occasions during the patient's clinical course did not change. The patient died from respiratory arrest six months after the initiation of therapy. To the best of the authors' knowledge, this combined form of disease, confirmed by both clinical and laboratory tests, is the rarest case ever to be reported.