An unusual case of neonatal myasthenia.

An unusual case of neonatal myasthenia gravis is reported in an infant who had respiratory failure due to diaphragmatic weakness. Although power and tone in the limbs were normal, fatiguability of both diaphragm and peripheral muscles was demonstrated. Acetylcholine receptor antibodies were absent in the mother, which suggests that an alternative humoral mechanism may have been responsible for the transient (6-week) neonatal weakness.