Better thymectomy outcomes with mild generalized myasthenia gravis
Disease severity was only factor that correlated with positive results
Patients with generalized myasthenia gravis (gMG) with mild pre-surgery muscle weakness had more favorable outcomes after a thymectomy, which involves the surgical removal of the thymus gland, than those with moderate or severe muscle weakness, a study finds.
In their study, “Pre-thymectomy disease severity predicts outcome in acetylcholine receptor antibody-positive generalised myasthenia gravis,” published in the Journal of Neurology, U.K. researchers investigated disease factors associated with good outcomes after removing the thymus gland, which is done to reduce the production of self-reactive antibodies.
Myasthenia gravis (MG) is an autoimmune disease caused by these self-reactive antibodies attacking the proteins involved in nerve-muscle communication. It’s commonly associated with abnormalities in the thymus gland, which produces immune cells.
A thymectomy is one of the therapeutic options for treating MG and is largely believed to decrease antibody production and reduce disease-related symptoms. The procedure is often recommended for MG patients with thymoma, that is, a malignant tumor in the thymus gland. While many people with MG benefit from the surgery, some don’t have positive outcomes, leading researchers to look at pre-surgery clinical characteristics between those who benefit from thymectomy and those who don’t.
Which gMG patients benefit most from thymectomy?
The researchers retrospectively analyzed data from 53 patients with gMG, confirmed self-reactive antibodies against acetylcholine receptors, and who had a thymectomy. The patients’ mean age at diagnosis was 45 and 43 were women. Twenty-seven patients had a thymoma.
The researchers looked at a number of clinical characteristics before surgery, including age at diagnosis, presence of thymus gland tumors, self-reactive antibody levels at diagnosis, time from diagnosis to thymectomy, disease severity (mild, moderate, or severe muscle weakness), and the use and dose of other medications.
Pre-thymectomy disease severity was the only factor that correlated with positive outcomes. Of the 53 patients analyzed, 37 had mild muscle weakness, pre-thymectomy and 11 had moderate weakness. Five patients had severe weakness.
At follow-up, 34 (64%) patients had good outcomes. Thirteen patients had no symptoms for at least a year without any therapy, called complete stable remission, 10 had no MG symptoms with some form of therapy, called pharmacological remission, and 11 had minimal manifestations, that is, no symptoms of functional limitations from MG, but some muscle weakness.
“The only variable that predicted less favorable outcome was disease severity before thymectomy. Patients with moderate or severe weakness … of muscles other than ocular muscles before thymectomy had a less favorable outcome,” wrote the researchers, who also compared the outcomes of the 27 participants with thymoma and the 26 without a tumor, and found having a thymus gland tumor didn’t predict a surgery’s outcome, in terms of remission rates or clinical manifestations. The researchers did note they may not have seen a relationship between tumor status and outcome because of the small sample size, however.
Due to the use of a long-term dataset, the researchers were able to investigate whether good outcomes after a thymectomy were lasting. On average, the time from a thymectomy to the last follow-up was nearly six years, giving the scientists important insights into which patient populations saw sustained benefits from surgery. Across different studies “there is a relatively consistent finding that pre-thymectomy disease severity is a predictor of outcome, which was confirmed in our study,” they said, adding “further validation in independent samples to assess any random effects is needed.”
Understanding the relationship between pre-surgery clinical characteristics and thymectomy outcomes can help patients and clinicians make informed decisions in treating gMG, the researchers said.
About the Author
