The findings of the study, “Impact of autoimmune comorbidity on fatigue, sleepiness and mood in myasthenia gravis,” were published in the Journal of Neurology.
MG is an autoimmune disease caused by the abnormal production of antibodies against proteins essential for muscle contraction. It is often associated with a series of debilitating symptoms, including muscle weakness, extreme fatigue, and sleep and mood disturbances.
As in other autoimmune diseases, MG patients are at higher risk of developing a second autoimmune disease.
“The prevalence of autoimmune overlap in MG ranges from 13% to 26%, with autoimmune thyroid disease (AITD), including Graves’ disease and Hashimoto’s disease, rheumatoid arthritis, systemic lupus erythematosus, and type 1 diabetes being the most frequent among 23 reported autoimmune comorbidities,” investigators said.
However, it is still unclear whether MG patients who have other autoimmune diseases experience severe symptoms, compared to those with MG alone.
In this study, researchers set out to examine the disease burden in MG patients who had at least one other autoimmune disorder.
Fatigue was assessed using the Fatigue Severity Scale (FSS) and the Fatigue Impact Scale (FIS); sleep disturbances were examined using the Epworth Sleepiness Scale (ESS); mood disturbances were assessed using the Beck Depression Inventory (BDI) and State-Trait Anxiety Inventory (STAI).
The study was based on a group of 69 MG patients who had been characterized in a previous study. Of these, 13 were found to have autoimmune thyroid disease (AITD) as well, and one patient had a third autoimmune disease (rheumatoid arthritis).
Analyses showed that a relatively high proportion of patients reported symptoms of fatigue (68.1%), excessive sleepiness during the day (14.5%), moderate to severe depression (20.3%) and anxiety (26.1%). However, the average FSS, FIS, ESS, BDI, and STAI scores were identical among patients with MG and other autoimmune diseases and in those with MG alone.
“We failed to verify our hypothesis — the level of these symptoms in MG patients did not appear to increase in the presence of a second autoimmune disease,” the investigators stated.
Although the presence of a second or third autoimmune disorder was not associated with significant changes in clinical and immunological MG characteristics, MG patients who had at least one other autoimmune disorder were more frequently treated with corticosteroids compared to patients who had only MG (92.3% versus 60.7%).
“Our results point to an intriguing association between steroid treatment and autoimmune comorbidity; while the higher frequency of steroid treatment in MG patients with autoimmune comorbidity might be primarily responsible for the lack of group differences in fatigue, sleepiness and mood disturbances, it also provokes speculation about a causal relationship between steroid treatment and occurrence of secondary autoimmune diseases in MG,” the researchers said.
“Due to the discussed limitations, we need larger prospective studies with comprehensive ascertainment of the most common autoimmune comorbidities to further explore our hypothesis, but also to elucidate the potentially far-reaching implications of steroid treatment in the development of secondary autoimmune diseases,” they said.