To describe the diagnostic and management challenges of severe transient neonatal myasthenia gravis (TNMG) in a late preterm infant with a significant family history.

TNMG is a rare, self-limited disorder affecting 10–15% of neonates born to mothers with myasthenia gravis (MG), due to transplacental transfer of maternal anti-acetylcholine receptor (AChR) antibodies. Clinical features include hypotonia, respiratory distress, and feeding difficulties, often mimicking other neuromuscular disorders. Family history and maternal disease severity may influence neonatal outcomes.

We report newborn delivered via emergent cesarean section for cord prolapse, born to a mother with MG and severe polyhydramnios. At birth, the infant was hypotonic, apneic, and cyanotic, requiring positive pressure ventilation. Neurologic exam showed profound hypotonia, absent suck and Moro reflexes, minimal spontaneous movement, preserved deep tendon reflexes, and left elbow arthrogryposis. Family history included a sibling with TNMG requiring IVIg and cholinesterase inhibitors. Laboratory evaluation revealed elevated AChR antibodies. A neostigmine trial led to clinical improvement, confirming TNMG. Management included respiratory support, pyridostigmine, and IVIg, with serial neurologic assessments and antibody monitoring. Plasmapheresis was considered but not performed due to limited evidence in neonates.

The patient gradually improved in tone, alertness, and respiratory function over several weeks. Respiratory support and cholinesterase inhibitors were weaned based on clinical status, with monitoring for side effects. Despite persistent thick secretions and intermittent respiratory setbacks, the patient showed progressive neurologic recovery. Antibody levels remained elevated but are expected to decline over 4–6 months.