Neuropediatrics 2004; 35 - P68
DOI: 10.1055/s-2004-819442

Congenital myasthenia with homozygotic mutation N88K of the rapsyn gene with infect associated respiratory insufficiency

U Gruber-Sedlmayr 1, M Brunner-Krainz 1, B Plecko 1, W Löscher 2, JP Sieb 3
  • 1University Childrens Hospital, Graz, Austria
  • 2Department of Neurology, Innsbruck, Austria
  • 3Max-Planck-Institute for Psychiatry Munich, Germany

Introduction: In the differential diagnosis of an infant with muscular hypotonia an impaired neuromuscular transmission must be considered. Numerous pathogenic mutations in various genes, encoding presynaptic, synaptic and postsynaptic proteins have already been identified. The clinical phenotype of patients with congenital myasthenic syndromes has a great variation.

Case report: K. is the second child of healthy parents, a brother deceased during a varicella infection at the age of 6 months. After an uneventful pregnancy K. was born at term. The neonate presented with joint contractures, muscular hypotonia and poor sucking. At the age of 7 months the girl required assisted ventilation for 3 days due to respiratory failure during a respiratory infection. At this time bilateral ptosis was noticed. The developmental milestones were achieved normally. At the age of 31 months a second respiratory failure occured due to bronchitis. After that event the diagnosis of myasthenia was suggested by the typical decrement on EMG, and a positive response to edrophoniumchloride. The diagnosis of a CMS was confirmed by molecular genetic analysis which revealed a homozygotic mutation N88K of the rapsyn gene.

Conclusion: The frequency of congenital myasthenia is probably underestimated. In infants with muscular hypotonia, joint contractures, respiratory failure postpartum and poor sucking, developing ptosis, a disorder of the neuromuscular transmission should be excluded. Congenital myasthenia has to be considered in the differential diagnosis of infect-related deaths of children and of SIDS. Due to therapeutic consequences an exact diagnosis of the defect is essential.

Keywords: congenital myasthenia, respiratory failure