Eaton-Lambert myasthenic syndrome

A 70-year-old woman without unusual medical history was admitted at a local hospital with complaints of fatigue, muscle weakness in the extremities and double vision. On examination, bilateral ptosis (figure 1), facial paresis, proximal-dominant limb muscle atrophy and generalized arreflexia were observed. On the basis of tentative diagnosis of myasthenia gravis, an electrodiagnostic study was conducted. It demonstrated abnormally low-amplitude muscular action potentials, but with a large increase after repetitive stimulation at 50 Hz. These responses are characteristic of the Eaton-Lambert myasthenic syndrome. A screening for malignant diseases was performed and chest radiography showed an anterior mediastinal mass (figure 2). The patient was scheduled for thymectomy, and subsequent histopathology of the thymus gland revealed a type B1 thymoma with areas reminiscent of a normal thymic cortex and medulla (figure 3). After the thymectomy most of the myasthenic symptoms were no longer in evidence. Generally, the Eaton-Lambert myasthenic syndrome is associated with small cell lung carcinoma, but this was an illustrative case associated with thymoma.