Transplacental passage of maternal antibodies to the unborn fetus has been described in several conditions including myasthenia gravis, immune thrombocytopenia, Graves disease, systemic lupus erythematosus, and pemphigoid gestationis. Transient and self-limited symptoms in the neonate, reflective of the maternal disorder, inculpate the antibody as pathogenic and serves as a natural passive-transfer experiment. This report describes a 36-year-old, G3, T1, P1, L2, female with seropositive AAG (1.33 nmol/L). Treatments with IVIg were stopped at the beginning of gestation. At term delivery, simultaneous maternal and fetal cord blood was sampled. The maternal and fetal ganglionic nicotinic acetylcholine receptor antibody (nACh-R Ab) level measured 0.31 and 0. 36 nmol/L, respectively. The baby, like his two older siblings, who were also born while the mother was symptomatic but undiagnosed, suffered from constipation, abdominal bloating, and delayed meconium passage. Daily bowel movements did not occur until 1-month post-partum. Orthostatic challenge was conducted via axillary suspension. Supine blood pressure (BP) measured 98/59 mmHg (MAP 70 mmHg) whereas suspended BP(after 15 minutes) dropped to 71/36 mm Hg (MAP 47). Serial ganglionic nACh-R Ab levels declined to 0.10 nmol/L by day 20 and 0.00 nmol/L by 3 months. This is the first report to confirm that (1) maternal ganglionic nACh-R Abs are capable of transplacental passage to the fetus, (2) neonatal ganglionic nACh-R Ab levels are measureable in both cord and venous blood, (3) the duration of symptoms correlates to the presence of the antibody, and (4) the half-life of the passive antibody complements timelines reported for both anti-MuSK and muscle nACh-R Ab-positive neonatal myasthenia gravis. Neonatal autonomic monitoring should be considered in the context of seropositive AAG mothers. Further case reports/series will clarify the incidence of passive NAAG and its correlation to Ab levels.
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