[A pregnant patient with anti-MuSK antibody positive myasthenia gravis and her infant with transient neonatal myasthenia gravis].

A 30-year-old healthy woman experienced speech disturbance and swallowing difficulty at two months of pregnancy. She was diagnosed as myasthenia gravis (MG) with anti-MuSK antibodies. At eight months of pregnancy, bulbar palsy, eye movement disturbance, and muscle weakness worsened unexpectedly. Plasma exchange was performed three times daily starting from the 1st day of the 37th pregnancy week (2 L/day, albumin substitution of 5%) and the patient underwent caesarean section and gave birth to the girl safely. The infant had anti-MuSK antibodies in the serum and umbilical cord blood. The infant's suckling power was weak. The infant was diagnosed as transient neonatal myasthenia gravis. There is no case where management of MG has been performed from the period of pregnancy for anti-MuSK positive patients. For the control of Anti-MuSK positive patients in addition to normal care for Anti-AChR antibodies positive patients, it is important to carefully observe symptoms caused by bulbar palsy, draw attentions on malnutrition and polyhydramnios, and perform simple plasmapheresis on regular basis without any delay.