Transient neonatal myasthenia gravis in a baby born to a mother with new-onset anti-MuSK-mediated myasthenia gravis.

We describe a 30-year-old pregnant woman with undiagnosed weakness who delivered a severely weak neonate. Subsequent workup of the mother revealed myasthenia gravis with muscle-specific kinase antibodies. The infant responded to intravenous immunoglobulin and symptoms normalized. He was presumed to have an anti-muscle-specific kinase-mediated transient neonatal myasthenia gravis.