Frédérique Truffaut works in the Myasthenia Gravis: etiology, pathophysiology & therapeutic approach team headed by Rozen Le Panse, within the Institute’s Center of Research in Myology. She has just published an article* in Science Reports on the specific features of juvenile myasthenia compared with myasthenia in adults.
In what context did you carry out this study, and what was its objective?
Our team works on myasthenia gravis (MG), an autoimmune disease linked to the presence of autoantibodies directed against components of the neuromuscular junction, mostly against acetylcholine receptors (AChR). It is characterized by abnormal skeletal muscle fatigability.
With the aim of better characterizing juvenile MG (JMG), we analyzed 85 pre-pubertal JMG and 132 post-pubertal JMG (with a cut-off age of 13 years) and compared them with 721 adult MG patients under 40 years of age from a French database we established between 1980 and 2019, under the direction of Dr. Sonia Berrih-Aknin. We compared our cohort with other JMG cohort studies conducted in several countries.
What methods did you use and what results did you obtain?
We analyzed clinical data, anti-AChR antibody levels, circumstances of thymectomy (whether it was performed, and if so, at what age), and thymic histology.
In terms of results, we found that the proportion of women was higher in each subgroup.
There were no significant differences in anti-AChR antibody levels. Interestingly, the proportion of AChR+ MG patients was significantly lower in adult MG patients aged 30 to 40, at 69.7%, compared with over 82.4% in the other subgroups.
Thymic histological data were examined in patients who had undergone thymectomy in the year of MG onset. Notably, in the prepubertal JMG group, the percentage of patients who underwent thymectomy was significantly lower (32.9% vs. over 42.5% in the other subgroups), and the time to thymectomy was twice as long.
We found a previously described positive correlation between anti-AChR antibodies and germinal center grade in all patient categories. What’s more, only women, particularly JMG patients, had the highest rates of lymphofollicular hyperplasia (95% of cases) and germinal center grade.
What conclusions did you draw?
These results reveal distinct patterns in JMG patients, particularly with regard to thymic follicular hyperplasia, which appears to be exacerbated in post-pubertal females, suggesting the potential benefits of thymectomy for pre-pubertal MG patients.
