[Response to immunoadsorption and steroid therapies in a patient with carcinomatous Lambert-Eaton myasthenia syndrome accompanied by disturbed consciousness].

A 75 year-old man developed gait disturbance and somnolence over a period of three months. Electroencephalography indicated theta slowing and cerebrospinal fluid (CSF) examination showed an increased cell count of 23/microliter and IgG of 7.2 mg/dl. He showed fatigue-inducing muscle weakness and the Harvey-Masland test demonstrated a low M-wave amplitude of 0.6 mV which increased to 3 mV with 50 Hz high-frequency stimulations. The serum titer of P/Q type anti-voltage-gated calcium channel (VGCC) antibody was quite high at 11,901 pmol/L (< 20 pmol/L). The patient was diagnosed as Lambert-Eaton myasthenia syndrome (LEMS) although at first no carcinoma was detected. Immunoadsorption therapy with a phenilalanine absorber column resulted in a reduction in the titer of anti-VGCC antibody to half of the initial concentration, but it increased again within several days. Six repeats of immunoadsorption and concomitant administration of prednisolone at a dose of 40 mg daily succeeded in reducing the anti-VGCC antibody titer of to below 390 pmol/L. The patient's consciousness disturbance and muscle weakness improved simultaneously over the next month and the lumbar puncture and electroencephalography showed normal results. Prednisolone administration was maintained at a dose of 30 mg daily and one year after occurrence of the first symptoms, a small cell lung carcinoma was detected. There was no evidence of limbic encephalitis such as an elevation of anti-Hu antibody in his CSF and serum or abnormal signal intensities in the hippocampal formations on MR imaging. The etiology of his disturbed consciousness remained unclear, but, in the case of LEMS, it could be a manifestation of a paraneoplastic syndrome associated with small-cell lung carcinoma. It is noteworthy that the anti-VGCC antibody titer rose to 1,262 pmol/L 2 months before his tumor was detected and decreased to 286 pmol/L after chemotherapy. P/Q type anti-VGCC antibody could therefore be a useful tumor marker reflecting activity of small-cell carcinoma.