Diagnostic difficulties encountered in the myasthenic syndrome sometimes associated with carcinoma

Six patients with the physiological features of the myasthenic syndrome associated with carcinoma are presented. The clinical features encountered in this group, including age, mode of onset, and duration of symptom indicate that it may escape detection owing to its resemblance to other neuromuscular disorders. Conventional concentric needle electromyography may lead to the disorder being confused with a myopathy. The association with carcinoma is by no means constant. Clinical and physiological improvement with guanidine is described in each case.