[A case of non-thymomatous refractory anti-AChR, Kv1.4 and titin antibodies positive generalized myasthenia gravis successfully treated by extended thymectomy].

A 74-year-old Japanese woman, who had been previously diagnosed as ocular myasthenia gravis (MG), presented to our hospital complaining of dropped head and increased fatiguability while eating. The edrophonium test was positive and decremental response was recorded on repetitive nerve stimulation. Her clinical presentation was compatible with generalized MG, and anti-AChR, Kv1.4 and titin antibodies turned out positive. Contrast enhanced CT scan showed no tumorous lesion such as thymoma. We initiated her treatment with a minimum dose of oral prednisolone. However, her condition got worse even after intravenous immune globulin and experienced myasthenic crisis twice, the former of which led to cardiopulmonary arrest. As she did not respond to traditional treatments, we determined to perform extended thymectomy. The histopathology showed atrophic change but her condition rapidly improved in several days after the operation, and soon she was weaned off the ventilator. Shortly thereafter her symptoms disappeared, followed by the titers of the antibodies above found all markedly decreased. It remains unclear how the atrophic thymus acted on the pathogenesis of refractory generalized MG.