Transient neonatal myasthenia gravis: refining risk estimate for infants born to women with myasthenia gravis.

OBJECTIVE Transient neonatal myasthenia gravis (TNMG) can render a neonate vulnerable to catastrophic respiratory depression. Our aim was to describe the clinical manifestations of TNMG, and to determine when the myasthenic signs become apparent in TNMG. METHODS We reviewed our own experience of infants who underwent routine inpatient monitoring for TNMG and combined our local data with observations from previous studies. RESULTS Only three case series (n = 110) reported both the type and timing of onset of myasthenic signs. Adding local data (n = 37) yielded 147 infants born to women with MG. Fifteen infants (10%) developed signs of TNMG with onset being 1.5 ± 2.6 days (mean ± 3SD) after birth. Feeding difficulties and low tone were the commonest presenting signs, and only 1 of the 147 infants needed intubation for hypoventilation. CONCLUSIONS TNMG signs were mostly not life-threatening. We suggest only 4 days of routine postnatal observation for infants born to women with MG.