Association of Arthrogryposis Multiplex Congenita with Maternal Antibodies Inhibiting Fetal Acetylcholine Receptor Function

Arthrogryposis multiplex congenita (AMC), characterized by multiple joint contractures developing in utero, results from lack of fetal movement. Some cases are genetically de-termined, but AMC occasionally complicates pregnancy in patients with myasthenia gravis (MG) suggesting involve-ment of circulating maternal antibodies. We previously demonstrated antibodies that inhibited the function of fetal acetylcholine receptor (AChR) in one healthy woman with an obstetric history of recurrent AMC. Here we study sera from this woman, from one other with a similar history, and from three (one asymptomatic) whose babies had neonatal MG and AMC. All five maternal sera had high titers of anti-bodies that inhibited