Patients and Controls
Between July 2019 and April 2021, 90
patients with MG were enrolled from
the Department of Neurology of the First Affiliated Hospital of Soochow
University. All patients were diagnosed with MG according to typical
clinical features, neostigmine tests, repetitive nerve electrical
stimulation, fatigue tests and positive acetylcholine receptor antibody
(AChR-Ab) results. Simultaneously, 36 healthy controls (HCs) matched to
patients with MG for sex, age, and race were enrolled from the
hospital’s physical examination center. The study subjects were excluded
if they had one of the following conditions: other autoimmune diseases,
acute infectious diseases, malignant tumor (except thymoma), mental
illness, or pregnancy or lactation. The quantitative MG score (QMG) was
used to assess the disease severity, and all patients received standard
treatment after admission to the hospital. The clinical characteristics
of the study subjects are shown in Table 1.
Patients with MG were classified into different subgroups based on sex,
age at onset, Myasthenia Gravis Foundation of America (MGFA)
classification, thymic histology, and AchR-Ab results. According to the
MGFA classification[16], patients were classified as having ocular
MG (OMG) or generalized MG (GMG). All patients underwent enhanced chest
computed tomography (CT)
examinations and were divided into an abnormal thymus group (with
thymoma or thymic hyperplasia) and a normal thymus group (without
thymoma or thymic hyperplasia). Due to the low positive proportion of
anti-MuSK antibodies in the Chinese population[17], the
concentrations of AchR-Ab (positive cut-off value was 0.45 nmol/L) were
detected in all patients with MG, and patients were divided into the
AchR-Ab-positive group and the AchR-Ab-negative group (cut-off value of
0.45 nmol/L).
Thirty-nine patients with untreated stage MG (USMG), 22 patients with
recurrence stage MG (RSMG), and 42 patients with paracmasis stage MG
(PSMG) were recruited from the Department of Neurology of the First
Affiliated Hospital of Soochow University between July 2019 and June
2021. USMG was defined as the first onset without treatment, including
glucocorticoids, immunosuppressants, plasma-exchange therapy or
intravenous immunoglobulins in the past 3 months. RSMG was defined as
the exacerbation of the original symptoms or signs or the recurrence of
symptoms after improvement. The duration of recurrence exacerbations
should be longer than 24 h, and the QMGs should be increased. PSMG was
defined as the absence of symptoms or signs of MG, with or without
weakness of eyelid closure, and no weakness of any other muscle upon
careful examination[18]. The demographic and clinical
characteristics of all study populations are summarized in