Ocular MG Progression Risk May Be Reduced With Immunosuppressants
Immunosuppressant medications significantly reduced the risk of ocular myasthenia gravis (MG), which affects only eye and eyelid muscles, progressing to a generalized form of the disease that affects other muscles, a Chinese study suggests.
These findings indicate that immunosuppressant medications should be considered early on in the treatment course of patients with ocular MG, who may fail to respond to other first-line therapies, according to the researchers.
The study, “Association of immunosuppression treatment with generalization among patients with ocular myasthenia gravis: a propensity score analysis,” was published in the European Journal of Neurology.
Eye muscle weakness, which manifests as double vision or eyelid droopiness, is the first symptom of MG in a majority of patients and is referred to as ocular MG. The disease is caused by the immune system wrongly attacking certain proteins involved in nerve-muscle communication.
In up to 80% of patients, MG progresses to a more generalized form wherein other muscles, such as those in the arms, legs, or involved in respiration, begin to be affected. This typically occurs within two years after the onset of ocular symptoms.
Previous observational studies suggest that patients on immunosuppressive therapies have a lower risk of disease progression to generalized MG.
Most of these studies, however, were based on a small sample size and mainly in Western populations, giving researchers an opportunity to see if immunosuppressives lower the risk of MG progression across different populations, including Asian patients.
Researchers in China analyzed clinical data of people with ocular MG who had been followed at seven medical centers in that country from January 2015 to May 2019.
They compared the rate of disease generalization between patients treated with immunosuppressants and those who were not over the first two years of disease onset.
Data analyzed covered 813 ocular MG patients, 425 (52.3%) of whom received immunosuppressants for at least three months within the first year of symptom onset. They had a mean age of 50 at ocular MG onset and 188 (44.2%) were women.
Immunosuppressants included either oral corticosteroids (prednisone) and/or non-steroidal immunosuppressants, such as azathioprine (245 patients), mycophenolate mofetil (14 patients), and tacrolimus (19 patients).
The remaining 388 patients (47.7%) were included in the non-immunosuppressants group. They had a mean age of 48.4 at disease onset and 185 (47.7%) were women.
All the patients were first treated with pyridostigmine (marketed as Mestinon, among other brand names), which is commonly prescribed to improve muscle strength. It specifically works by increasing the availability of acetylcholine, a chemical normally released by nerve cells that causes muscle cells to contract.
Those who failed to respond to pyridostigmine were prescribed immunosuppressants.
Patients treated with immunosuppressants had a higher rate of double vision (44.7% vs. 35.1%). More patients in the non-immunosuppressants group had a thymoma (31.8% vs. 14.9%), and more had a thymectomy prior to disease generalization (29.2% vs. 17.9%).
A thymectomy is a surgical procedure to remove the thymus gland, an organ of the immune system thought to be involved in producing self-reactive antibodies in MG. In some patients, autoantibody production is accompanied by a tumor, called a thymoma.
A total of 122 patients (31.4%) in the non-immunosuppressants group progressed to generalized MG compared with 37 patients (8.7%) in the immunosuppressants group. MG generalization also occurred faster among non-immunosuppressants patients than those given immunosuppressants — within a median of 9.5 months of disease onset compared with 12 months.
The risk of progression to generalized MG was always lower with immunosuppressants in two different statistical analyses.
Over two years, the rate of MG generalization was markedly lower among patients in the immunosuppression group compared with those in the non-immunosuppressants group (10.8% vs. 32.0%).
Further analyses linked longer treatment with immunosuppressants with a lower risk of generalization. A lower rate of disease generalization at two years (5.8% to 20.1%) was also seen when a combination of steroids and non-steroidal immunosuppressants were used instead of steroids alone.
Overall, these findings showed that treatment with immunosuppressants “significantly reduced the 2-year risk of generalization in patients with [ocular MG], suggesting that immunosuppression should be considered earlier in the treatment algorithms for [ocular MG],” the researchers wrote.
“Further randomized controlled trials with a better level of evidence are warranted to confirm the risk-modifying effect of immunosuppression in such patients,” they added.