Discordant spectrum of cardiac manifestations of neonatal lupus in twins.

Congenital complete heart block associated with transplacental passage of maternal autoantibodies reactive with SSA/Ro and SSB/La is a rare disease with significant fetal, neonatal, and childhood morbidity and mortality. We present the case of dichorionic, diamniotic twins (female twin A and male twin B) exposed to maternal Ro and La autoantibodies with different disease expression. Twin A (female) had Mobitz type I second degree atrioventricular (AV) block (Wenckebach); twin B (male) had normal sinus rhythm. Both twins had structurally normal hearts but demonstrated echocardiographic evidence of endocardial fibroelastosis (EFE). Following maternal dexamethasone 4 mg once daily, twin A reverted to sinus rhythm in utero; twin B remained in sinus rhythm throughout pregnancy. Echocardiograms after delivery demonstrated resolution of EFE in both fetuses, and EKGs confirmed sinus rhythm. However, at five months of age, Holter monitor demonstrated first degree AV block and intermittent Wenckebach in twin A. Twin B remains in sinus rhythm. This case is one of only three in the literature that describes Mobitz type I second degree atrioventricular block presenting in fetuses exposed to maternal SSA and SSB autoantibodies and is the first case that we have seen reported in twins. Importantly, this case also adds to the growing body of literature describing EFE as a presentation of neonatal lupus with or without conduction system abnormalities, emphasizes the spectrum of cardiac conduction abnormalities in neonatal lupus syndrome, and raises interesting questions about discordant disease expression in twins.