Clinical Characteristics of Childhood-Onset Myasthenia Gravis in a Large Chinese Cohort

Among the new cases of myasthenia gravis in China, the proportion of new childhood-onset myasthenia gravis (CMG) patients ranges from 10.3% to 12.6% and is increasing annually. Nevertheless, it remains a rare disease with limited extensive cohort studies. This study aimed to summarize and describe the clinical characteristics of CMG patients in China.

We reviewed the data from CMG patients treated at the Center for Myasthenia Gravis in Hebei Province between 2013 and 2023 and finally included data from 1031 patients.

The gender ratio (male: female) was 1:1.4 and the median age of onset was 5 years, with a single peak at ages 1-3 years. Within the cohort, family history accounted for 1.7% (18/1031) of the patients. Furthermore, common cold was the most prevalent medical history factor in the cohort, accounting for 4.8% of the total patients. Overall, 62.4% (643/1031) and 0.5% (5/1031) of patients tested positive for acetylcholine receptor antibodies (AChR-Abs) and muscle-specific kinase antibodies (MuSK-Abs), respectively. In addition, the AChR-/MuSK-Ab-double positive rate was 0.1% (1/1031), whereas that for MuSK/AChR-Ab double negativity was 37.25% (384/1031). The Myasthenia Gravis Foundation of America (MGFA) I classification grade was high across all age groups, with the remaining classification grades increasing with age. In addition, ocular weakness as an initial symptom was high across all age groups, and as the age of the patients increased, the proportion of patients with weakness in the limbs, bulbar, and respiratory also increased. Finally, the AChR-Ab titer level was lowest in patients with MGFA I classification and may be related to prognosis.

CMG has a peak incidence at ages 1-3 years, with some familial predisposition and a predominance of high MGFA I classification and AChR-Ab positivity. The complexity of the initial symptoms in CMG patients is related to increasing age. Interestingly, the AChR-Ab titer levels may be a potential factor in predicting patient prognosis.