Clinical features, serum acetylcholine receptor antibody (AChRAb) titr
es and course were reviewed in a series of 25 congenital (CMG) and 30
juvenile (JMG) myasthenia gravis cases to recognize characteristics of
childhood-onset myasthenia and its subgroups. The initial symptom for
CMG is ptosis accompanied or followed by generalized weakness; myasth
enic crises do not occur and spontaneous remissions are rare. In JMG,
the distribution of weakness remains the same, but the severity fluctu
ates: spontaneous remissions (6 patients) and myasthenic crises (10 pa
tients) are observed. Good response to anticholinesterase drugs is sli
ghtly more frequent in JMG (62 versus 41%). AChRAbs were present in 9/
26 JMG tested, girls with onset after 11 years being more likely to be
Ab-positive. Since patients with autoimmune myasthenia and a young ag
e of onset are often seronegative, clinical features such as changing
distribution of weakness, fluctuating severity, or response to treatme
nt might be considered as supportive criteria for differentiating JMG
from CMC.