Thymectomy Seen to Aid Remission in Ocular MG Patients Younger Than 40

People who develop ocular myasthenia gravis (OMG) before age 40 are more likely to go into remission after surgery to remove the thymus (thymectomy), according to a Chinese study.

The work also supported thymectomy as a safe and effective approach to treat OMG, with about 40% of patients achieving complete and stable remission five years after surgery.

Such findings may help physicians make better treatment decisions, but larger studies are needed to confirm whether age at OMG onset predicts disease remission after thymectomy, the researchers said.

The study, “Prognostic predictors of remission in ocular myasthenia after thymectomy,” was published in the Journal of Thoracic Disease.

Problems with immune system regulation and tumors in the thymus — a gland located in the chest that regulates the development of immune cells called T-cells — are associated with the development of myasthenia gravis (MG).

A large body of evidence suggests that thymectomy is an effective way of treating or lessening symptoms of MG, and previous studies even suggest that it may be more effective than pharmacologic approaches in inducing MG remission.

However, the role of thymectomy in ocular myasthenia gravis, a type of MG that affects only the muscles controlling the eye and eyelid, remains controversial. Since most OMG patients develop generalized MG within two years of a diagnosis, understanding the effectiveness of this surgery in OMG remission is relevant.

While few reports focus on the specific role of thymectomy in OMG, a previous review study suggested that it was a safe and effective in this patient population.

Since it is unlikely that thymectomy will be effective for every OMG patient, identifying predictors of such success is key to selecting those most likely to benefit from surgery and avoiding exposing others to unnecessary risks.

Researchers at University of South China set out to identify potential predictors of disease remission after thymectomy in 51 OMG patients (28 women and 23 men) who underwent surgery between 2011 and 2017 at the university’s Second Affiliated Hospital.

The team said that thymectomy was typically only recommend to OMG patients if they had thymomas (tumors of the thymus), if immunosuppressive treatments were not able to control symptoms, or if there was a need to avoid or reduce the use of such medications.

In this study, patients were asked to make their own decision regarding surgery after the pros and cons of both pharmacologic and surgical approaches were explained.

Clinical outcomes were assessed using the Myasthenia Gravis Foundation of America Post-Intervention Status (MGFA-PIS). Complete stable remission was defined as no symptoms and no need for medication for at least one year.

Patients’ median age at disease onset was 40 (range 5–79 years). They were followed for a median of 45 months after surgery (slightly under four years), with a maximum follow-up of 93 months (under eight years).

Nine of these 51 patients (17.6%) had a thymoma.

Results showed that those with thymoma developed OMG at a significantly older age (61 vs. 33.5 years), had a significantly shorter disease duration before undergoing thymectomy (3 vs. 10 months), and showed a significantly higher rate of postoperative complications (44.4% vs. 9.5%).

All survived surgery, and 41.8% of these patients achieved complete stable remission five years after thymectomy. Complete remission rose to 48.3% among patients without thymoma, suggesting this approach is also effective for this patient group.

Age at disease onset was significantly associated with remission after surgery, with patients up to age 40 being nearly four times more likely to achieve disease remission than those who developed the disease at an older age. No other remission predictors were identified.

“Our results further confirmed the safety and efficacy of thymectomy in patients with OMG,” the researchers wrote, adding that “minimally invasive thymectomy should be recommended to OMG patients with diplopia [double vision] impairing quality of life and unsatisfactory response to adequate immunosuppressive medications.”

However, studies with larger number of patients and followed at different clinical centers are needed to confirm their findings and to potentially identify other predictors of OMG remission after thymectomy, they added.