Lambert-Eaton myasthenic syndrome (LEMS) is an immunological disease known to be associated with malignant disease, and is characterized by muscle weakness and autonomic neuropathy. Small cell lung cancer is one of the most important causes of this condition. We encountered a case of LEMS associated with small cell lung cancer presenting with dry mouth.
A 65-year-old man visited to our hospital with the complaints of dry mouth, muscle weakness of the lower limbs and gait disturbance. The patient showed significant hyposalivation, however, the diagnosis of Sjogren’s syndrome could not be established based on the results of minor salivary gland biopsy and blood tests. Chest CT showed a nodular lesion in the left lung and swollen lymph nodes in the mediastinum. In regard to the neurological findings, the patient showed hyporeflexia, and lower limb weakness. Therefore, we suspected the possibility of LEMS associated with lung cancer. Video-assisted thoracic surgery was performed, and small cell lung cancer was diagnosed based on histopathological examination of the resected specimen. Five courses of chemotherapy (cisplatin+etoposide) and concurrent radiotherapy at a total dose of 45 Gy were administered, which resulted in a complete response.
Autonomic neuropathy such as that associated with LEMS should be borne in mind in the differential diagnosis of dry mouth.
