Thymoma, age, disease severity tied to high myasthenic crisis risk: Study
Researchers: Findings show importance of evaluating disease severity in clinical practice
People with myasthenia gravis (MG) who have more severe disease when they are diagnosed, are older at its onset, or have a thymus tumor are at a higher risk of myasthenic crises, a study from Southwest China indicates.
According to the researchers, “the results underscore the critical importance of evaluating disease severity in clinical practice for individuals with MG, as it not only aids in guiding clinical management, but also assists in assessing the risk associated with [myasthenic crises] occurrence.”
The study, “Risk Factors for Myasthenic Crisis in Patients With Myasthenia Gravis: A Retrospective Study in Southwest China,” was published in the International Journal of Clinical Practice.
MG is caused by self-reactive antibodies attacking proteins needed for the proper function of the neuromuscular junction, where nerve cells and muscles communicate to coordinate voluntary movements. These antibodies most commonly target acetylcholine receptors (AChRs) on muscle cells, but can also target other proteins, including muscle-specific kinase (MuSK).
This leads to muscle weakness and fatigue, the disease’s hallmark symptoms. When muscle weakness affects respiratory muscles, patients may have a a potentially life-threatening complication marked by severe breathing difficulties, or myasthenic crisis, that requires hospitalization and mechanical ventilation.
Myasthenic crisis risk factors
To know more about potential risk factors for myasthenic crises, researchers retrospectively studied MG patients in Southwest China, using the MG Cohort Database at the West China Hospital of Sichuan University. Eligible patients included those who’d received a definitive MG diagnosis between January 2004 and August 2023.
A total of 1,150 patients who had a mean age at disease onset of 42.5 and mainly women (59.7%), were included. Most had early-onset disease (63.9%) and generalized MG (67.3%). More than half (60.7%) were tested for self-reactive antibodies, with about three-fourths (71.6%) receiving a positive result, most having anti-AChR antibodies (67.5%).
Regarding treatments, most patients received corticosteroids (78.5%), followed by immunosuppressants (38%). Cholinesterase inhibitors, medications that prevent the destruction of acetylcholine — a chemical messenger crucial for nerve-muscle communication — were used exclusively by 8.4%.
Over about five years of follow-up since their diagnosis, 128 (11%) patients had at least one myasthenic crisis.
Those patients were older at the time of the onset of their disease (46.8 vs. 41.9 years), and most commonly had gMG (82% vs. 65.5%) and more severe disease, as assessed by MG Foundation of America (MGFA) and quantitative MG (QMG) scores. The prevalence of thymus tumor, or thymoma was also higher (31.3% vs. 10.5%).
Several risk factors were significantly associated with a higher myasthenic crisis risk. For instance, having a more severe disease at diagnosis according to the MGFA score and a thymoma increased the risk of having a myasthenic crisis by more than three times. Also, being older or having a higher QMG score at diagnosis increased the risk by 2% and 4%, respectively. Although there was a trend toward an increased risk associated with the presence of anti-MusK antibodies, the difference didn’t reach statistical significance.
“This single-center retrospective study identified age of onset, disease severity … and the presence of thymoma as independent risk factors for the occurrence of [myasthenic crises] in Southwest Chinese patients with MG,” the researchers wrote. “These findings provide significant evidence for predicting the likelihood of [myasthenic crises] in this patient population … [and] underscore the critical importance of evaluating disease severity in clinical practice.”
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