A neuromuscular transmission block produced by a cancer tissue extract derived from a patient with the myasthenic syndrome.

The myasthenic syndrome occasionally is associated with bronchogenic carcinoma. The neuromuscular transmission defect in this syndrome is characterized by a reduction of acetylcholine release from motor nerve endings. This paper reports that an acetone extract of cancer tissue from a patient with the syndrome reduces the acetylcholine release from motor nerve endings and produces a neuromuscular transmission defect in the frog nerve-muscle preparation. This suggests that the pathogenic substance(s) contained in the extract may be produced by certain types of bronchogenic carcinoma and may cause the myasthenic syndrome.