Abstract
Recently we treated two patients with transient neonatal myasthenia gravis. The serum samples of one patient and her mother were examined for anti-acetylcholine receptor (anti-AchR) antibody by radioimmunoassay system using anti-human IgG serum.
The infant, a 2500 gm male baby, was delivered at term from a 27-year-old primiparous myasthenic mother to whom had been prescribed ambenonium chloride for three years. He required immediate intubation because of poor respiratory effort and falling heart rate, but his myasthenic symptoms disappeared after the administration of neostigmine bromide. He was discharged on 27 days of life without any recurrence of symptoms and given no medicine. Anti-AchR antibody in his serum was not measured.
Another infant, a 2620 gm female baby, was delivered at term from a 30-year-old multiparous woman who had had generalized myasthenia gravis for seven years. The mother was successfully treated with ambenonium chloride. Her first delivery was uneventful, but the myasthenic symptoms of the mother relapsed immediately after delivery. Therefore, thymectomy was performed and she was given ambenonium chloride daily throughout second pregnancy. The patient appeared to be normal at birth. One day after birth, however, she was observed to be weak in sucking and developed respiratory difficulty. Edrophonium chloride test was positive and she was given oral neostigmine bromide with satisfactory control of symptoms. Medication was completely discontinued at 30 days without any recurrence of symptoms. She was discharged on 34 days of life and appeared perfectly normal, The anti-A chR antibody titer in baby's serum gradually fell from 2.19 pmoles/ml at 4 days to 0.73 pmole/ml at 15 days and 0.38 pmole/ml at 20 days concomitant with the amelioration of myasthenic symptoms. On the other hand, high titer of anti-AchR antibody (3.42 pmoles/ml) was detected in the serum of the mother at delivery.
These findings suggested that the nature of the disorder might be due to placental transmission of anti-AchR antibody.
