Artrogryposis multiplex congenita -- a rare fetal condition caused by maternal myasthenia gravis

To look at the occurrence of arthrogryposis multiplex congenita in newborn of mothers with myasthenia gravis (MG) and factors connected to this.

We retrospectively studied 176 births by 79 MG mothers, recorded in the Medical Birth Registry of Norway (MBRN). Four (2.2%) newborns (including one pair of twins) born with severe skeletal anomalies were identified.

All four children died. Three had findings consistent with arthrogryposis multiplexa congenita (AMC), one had a fetal akinesia deformation sequence (FADS). The mother of the child with FADS had previously given birth to a child with neonatal MG. She was now in complete MG remission. The mother of the twins with AMC later gave birth to a child with neonatal MG.

Siblings of an affected child -- either with neonatal MG or AMC -- have an increased risk to develop either neonatal MG or AMC. As this appears to be independent of the MG mother's clinical state, it is important to discuss previous pregnancy outcomes with all female MG patients.