Older Late-onset Patients Have Overall Positive Prognosis

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by Vanda Pinto |

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Patients who start experiencing symptoms of myasthenia gravis (MG) after age 65 have an overall good prognosis and response to immunosuppressive treatments, according to a recent Canadian study.

In addition, the presence of other medical conditions, or comorbidities, had no effect on the severity of MG symptoms or on the clinical outcomes of these patients.

The study with those findings, “Clinical profile and impact of co-morbidities in patients with very-late onset myasthenia gravis,” was published in the journal Muscle & Nerve.

MG is traditionally considered to be late-onset when it develops after the age of 40, although some studies have suggested a cut-off age of 50 to distinguish early from late-onset disease. Patients who experience MG for the first time

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after age 65 are currently classified as having very-late-onset MG.

These patients are prone to develop a more widespread form of the disease, known as generalized MG, and usually have less need for long-term maintenance therapy with immunosuppressive medications. Patients with late onset-MG may have a life-threatening crisis at disease onset, but normally show lower treatment resistance.

Researchers in Canada reasoned that comorbidities, type of medications, and a decline in physical and/or cognitive functioning associated with old age, could affect the clinical profile of  patients with very-late-onset MG. In addition, since older patients often take several medications, it is possible  these could worsen MG symptoms or interact with those used to treat MG.

To investigate this further, the research team analyzed data from MG patients age 65 and older at symptom onset, who attend the Prosserman Family Neuromuscular Clinic at Toronto General Hospital from 2015 to 2020.

Analyzed data included demographics, clinical profile and severity, antibody profile, imaging studies, comorbidities, and prescribed medications. Patients  also were divided and placed into 10 category groups, depending on the presence and type of comorbidities.

Two measurements of disease severity were used, including the Myasthenia Gravis Foundation of America (MGFA) severity scale and the Myasthenia Gravis Impairment Index (MGII).

Outcome measures were determined with the MGFA Post Intervention Status (MGFA-PIS) and Simple Single Question (SSQ). Patient clinical outcomes were classified as improved, unchanged, and worsened by comparing scores obtained at their last visit to those seen at their first visit.

Of a total of 109 patients, 90 had more than one follow-up visit. Mean duration of follow-up was almost five years and the mean age of the patients was 75. About 68% of patients had generalized MG and 66% had more than one comorbidity.

More than two-thirds (71%) of patients improved over the course of follow-up, entering in remission or having minimal disease manifestations. In addition, more patients with generalized MG compared with those with ocular MG remained unchanged (10% vs. 2%) or worsened (16% vs 1%) at their last follow-up visit.

The team then used statistical models to analyze the associations between several MG-relevant parameters and prognosis.

Results showed no association between factors such as age, duration of symptoms before diagnosis, duration of follow-up, MGFA score, medications, comorbidities, or crises and final outcome. The presence of other comorbidities had no impact on the MGII.

“None of the demographic factors or comorbidities showed an association with MGFA-PIS, SSQ or MGII after correction for multiple comparisons,” the authors wrote.

Although a third of patients in the study were taking medications that are known to worsen MG, such as statins and beta-blockers, these medications did not appear to have a negative impact on their final clinical outcome.

By the end of the last visit, 25% of patients reached either complete stable or pharmacological remission and less than 20% needed two or more immunosuppressive medications to manage their condition. Of note, complete stable or pharmacological remission typically refer to a status in which a patient ceases to experience MG symptoms while receiving minimal or no MG treatment for a given period of time.

“We found that patients with very-late onset MG have favorable long-term outcomes with good response to immunosuppressive medications. No comorbidities significantly influenced the outcomes,” the authors concluded.

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