We report a 64-year-old man diagnosed with
Lambert-Eaton myasthenic syndrome (LEMS) associated with pulmonary
squamous cell carcinoma. Circulating anti-P/Q-type voltage-gated
calcium channel (VGCC) antibody was detected, and the patient was treated with
3,4-diaminopyridine. At age 61, chest radiograph revealed a
tumor shadow in the right upper lung field. This was surgically removed, and a histological diagnosis of moderately differentiated pulmonary
squamous cell carcinoma was obtained. After about 1 year, mediastinal
metastasis was detected and
5-FU was administered. Eight months later,
metastasis was noted in the left frontal hemisphere, and radiosurgical
therapy was performed. The
brain tumor gradually shrank but generalized
fatigue, thirst, and gait disturbance developed after 4 months. A diagnosis of LEMS was made on the basis of neurological findings including proximal
muscle weakness and absent tendon reflexes; autonomic symptoms (thirst,
constipation, and
impotence); characteristic electromyographic findings; and circulating anti-P/Q-type VGCC antibody. He has been treated with
3,4-diaminopyridine at a dose of 30 mg/day, resulting in marked improvement in symptoms but little change in electromyographic findings. The present case is very rare and suggests that anti-P/Q-type VGCC antibody may be involved in the mechanism of LEMS associated with pulmonary
squamous cell carcinoma.