Salbutamol-responsive fetal acetylcholine receptor inactivation syndrome

Transient neonatal myasthenia gravis (TNMG) is a rare and usually self-limiting condition due to maternal acetylcholine receptor (AChR) antibodies in neonates born to mothers with myasthenia gravis (MG). However, a skeletal myopathy with consistent and recognizable features (fetal acetylcholine receptor inactivation syndrome [FARIS]) was recently reported in some patients.1,2 FARIS occurs in association with clinically manifest maternal MG or asymptomatically elevated maternal AChR antibodies directed against the fetal AChR γ subunit. While in utero antibody exposure is considered the main pathogenic mechanism, the timing and intensity of maternal MG treatment plays an important role in determining fetal and postnatal outcome.1 Acknowledgment: The authors thank the patient's parents for their participation and consent to publication of clinical photographs; Dr. Leslie Jacobson for antibody testing; and Dr. Darryl de Vivo, New York, NY, for stimulating discussions.