Sex differences found in MG symptoms, surgery outcomes: Study
Women have MG symptoms earlier, face longer diagnostic delays than men
Women who have surgery to remove their thymus gland to treat myasthenia gravis (MG) tend to have experienced symptoms earlier in life than men, but waited longer to receive a diagnosis, a study reports.
However, after the surgery, called a thymectomy, female patients have higher rates of complete remission and require fewer in-hospital treatments than male patients.
“There are sex-related differences in symptoms at MG onset, length of diagnostic delay, and prognosis during post-thymectomy follow-up, the origins of which should be further studied,” researchers wrote.
The study, “Differences Between Females and Males in the Diagnostic Delay and Clinical Course of Thymectomised Myasthenia Gravis,” was published in the European Journal of Neurology.
In MG, an autoimmune reaction disrupts the normal communication between nerve cells and muscles, resulting in muscle weakness and other symptoms. The disease is considered to be early onset when it appears in people younger than 50 years, and to be late onset when it manifests in those older than 50.
Sex differences in MG diagnosis, prognosis found in previous research
While the specific causes underlying the autoimmune response that drives MG aren’t entirely understood, abnormalities in the thymus gland, an organ that’s part of the immune system, may play a role. Sometimes, MG is associated with a tumor in the thymus. A thymectomy may help resolve symptoms for some patients.
Some studies have found sex differences in MG diagnosis and prognosis, but results haven’t been conclusive, according to the team. To address these questions within the constraints of a retrospective study, the researchers developed a methodology to control as many variables as possible.
“Taking into consideration clinical heterogeneity and variability of treatment methods in MG, we sought to balance these confounding factors by studying a cohort of thymectomized MG patients in a single center with an extensive follow-up time,” they wrote.
In the study, they identified a total of 251 people with MG (124 male and 127 female) who had undergone a thymectomy and received care at a hospital in Helsinki, Finland.
Female patients experienced their first MG symptoms at a mean age of 35.9 years, and 74.8% had early-onset MG. Male patients were significantly older at symptom onset, with an average age of 55.9 years, and 73.4% had late-onset MG.
Higher percentage of women first experience symptoms of generalized MG
At the time of disease onset, about half of the men had symptoms of ocular MG, a form of the disease limited to the muscles controlling eye and eyelid movements, while the other half had symptoms of generalized MG, a more severe form marked by widespread muscle weakness.
Among women, however, 70.9% first experienced symptoms of generalized MG. Despite having an earlier and more generalized symptom onset, women tended to wait longer for a diagnosis, with a median diagnostic delay of six months. Men received a diagnosis a median of 3.2 months after experiencing their first symptoms.
Within a subgroup of 195 patients with generalized MG unrelated to thymus tumors, women had better clinical outcomes after undergoing thymectomy. Greater proportions of women were in complete stable remission (no signs of active disease while not taking any MG medication) at their last recorded visit compared with men (17.1% vs 4.5%). Additionally, fewer women needed in-hospital treatments or immunosuppressants after having surgery.
Statistical analyses also indicated people who were younger when they first experienced symptoms were more likely to achieve complete stable remission. However, the likelihood of attaining remission was not influenced by diagnostic delays or the type of initial symptoms patients experienced.
“Better thymectomy response for females with [generalized MG] in our study may reflect that females were younger at the time of diagnosis and more often had [early onset MG],” the research team wrote, noting the underlying causes of the sex differences they identified merit further study.
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