Treatment of myasthenia gravis: a comparison of the natural course and current therapies.

Ninety-five patients with generalized myasthenia gravis were followed for 10 years to evaluate the long term effects of prednisolone, thymectomy, or both, and they were compared with a group only with anticholinesterase treatment. Only 15.0% of the patients with anticholinesterase alone had showed improvement 10 years after the onset, but more than 60% of those treated with prednisolone, thymectomy, or both showed improvement. Especially thymectomy induced complete remissions at 10 years after surgery in more than 20% of the patients. There was no difference between the histology of the thymi and clinical severity, or anti-acetylcholine receptor (AChR) antibody titer. In patients who showed improvement classified "good" of higher 10 years after thymectomy with or without prednisolone, anti-AChR antibody titers swiftly decreased to 37.8% of the value before surgery, and remained low thereafter. This result suggests that the marked decrease in anti-AChR antibody titers within 1 month after thymectomy is a favorable prognostic sign in myasthenia gravis patients who have undergone thymectomy.