A TRANSIENT NEONATAL MYASTHENIC SYNDROME WITH ANTI-MUSK ANTIBODIES

Abstract

Some patients with myasthenia gravis (MG) have autoantibodies to muscle specific kinase (MuSK) instead of the acetylcholine receptor (AChR). Anti-AChR antibodies may be transferred across the placenta causing a self-limiting neonatal myasthenic syndrome. We describe an infant with a similar disorder whose mother had MuSK MG. ### Case report. In September 1994, the mother noticed unilateral ptosis and a feeling of generalized fatigue at age 13. Over the next months, she developed severe oculobulbar weakness, dyspnea, and weakness of the neck. Symptoms were fluctuating and unresponsive to acetylcholinesterase inhibitors. No antibodies to the AChR were found. In 1995, a normal thymus was removed. High doses of prednisone had little effect. In 1997, plasmapheresis induced a partial remission and this became her regular therapy for several years. In 2004 anti-MuSK antibodies were found. She had two first trimester miscarriages while using pyridostigmine and prednisone in September and December 2004. In May 2005, she became pregnant using only prednisone 20 mg on alternating days. This pregnancy was uneventful without large fluctuations of her myasthenic symptoms. In February 2006, at 38 + 1 week of gestation, she unaidedly delivered a boy in head position. Apgar score was 10 after 1 and 5 minutes. Birthweight was 3,190 g (P25). Physical examination was unremarkable. After 8 hours, however, drinking became difficult. After 16 hours, he showed mild generalized hypotonia with diminished facial expression …