G.P.72 Myasthenic symptoms: From initial presentation to diagnosis

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Abstract

Transient neonatal myasthenia gravis arises from antibody mediated maternal disease during pregnancy. Clinical findings vary from postnatal muscular weakness up to arthrogryposis multiplex congenita (AMC). If AMC is associated with polyhydramnios, pulmonary hypoplasia, dysmorphic facial features and central nervous abnormalities it belongs to a fetal akinesia, namely Pena-Shokeir-phenotype. Diagnosis allows therapy for the child and in further pregnancies for the mother. The boy was presented to our clinic as a “floppy infant” at the age of 8 months for adjustment of a nocturnal non-invasive ventilation. Extensive diagnostic procedures had been performed previously – including a muscle biopsy – overall not leading to diagnosis. The examination showed retrognathia, contractures of the fingers and pulmonary hypoplasia. Analyses revealed acetylcholinreceptor-antibodies (AChR-AB) elevated with >1 nmol/l, consequently a therapy with pyridostigmine was initiated leading to a significant improvement of respiratory situation and motor development. Now the boy is three years old, walks and eats independently, but lacks development of speech so far. The mother presented mild muscular weakness of the shoulder girdle and elevated AChR-AB of 5.6 nmol/l. She has clinically and neurophysiologically no myasthenic symptoms. Pyridostigmine treatment did not generate an amelioration. A specific analysis of AChR-AB from the mother in Oxford disclosed antibodies against the fetal subunit of the AChR. In patients presenting with a Pena-Shokeir-phenotype myasthenia must be considered, caused by maternal antibodies against the fetal subunit (gamma) of the AChR, which is expressed in fetuses until the 32nd week of gestation. The diagnosis is crucial for the treatment of the child and further pregnancies of the mother. Fetal impairment can be avoided through thymectomy before and immunosuppressive treatment during pregnancy to suppress the producing of the antibodies.

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