Newborn infants to myasthenic mothers: a clinical study and an investigation of acetylcholine receptor antibodies in 17 children.

We studied 17 children born to 15 myasthenic mothers; 2 of the infants had neonatal myasthenia gravis. Pyridostigmine was transferred to the child and accumulated in the amniotic fluid. Sixteen children had receptor antibodies at birth. In the affected infants, the half-life of the receptor antibody concentration was longer than it was in the others. Using an anti-idiotypic antibody, we found marked differences between the idiotypes in the mother and in affected children. Transient synthesis of receptor antibodies in the child seems to be a factor in the pathogenesis of neonatal myasthenia gravis.