Transient Neonatal Myasthenia Gravis: A Case Report

Myasthenia gravis (MG) in the neonate is usually due to placentally transferred antibodies to the acetylcholine receptor (AChR), resulting in impaired neuromuscular transmission. It occurs in 10%-15% of newborns born to women with MG. We present a male newborn admitted to the neonatal intensive care unit (NICU) 38 hours after birth due to feeding difficulties and choking episodes. He was born to a mother with MG after an uneventful, well-followed pregnancy. Physical examination revealed a weak cry, persistent inability to fully close his eyelids, weak facial mimic, and a mouth that was always held open with swallowing and sucking difficulties. He assumed a frog leg position and showed generalized hypotonia with marked head lag. No respiratory distress was present. Laboratory evaluation showed an elevated anti-acetylcholine receptor antibody concentration (36.30 nmol/L; normal: <0.25 nmol/L). Transient neonatal myasthenia gravis (TNMG) was admitted, and an anticholinesterase agent was initiated. Given that he showed only a mild clinical improvement, two doses of immunoglobulin were administered on the eighth and ninth days of life. Anticholinesterase agents were progressively reduced and suspended on day 31 of life with clinical improvement. He was discharged home at one month of life clinically asymptomatic. He was evaluated one month later and was doing well. A positive history of MG in the mother associated with a suggestive physical examination may be sufficient to make the diagnosis of transient neonatal MG, emphasizing the importance of good medical history. With prompt diagnosis and appropriate management, most newborns experience spontaneous remission after a period of weeks to months.