Neonatal lupus syndromes

Neonatal lupus continues to generate considerable interest despite its rarity; more than 15 original contributions were made to the literature in the past year. Diverse aspects of this "syndrome" of passively acquired autoimmunity have been covered. Experiments using a rabbit model provided insights into the pathogenicity of maternal anti-Ro/SS-A and anti-La/SS-B antibodies. Perfusion of rabbit hearts with anti-Ro/SS-A and anti-La/SS-B sera resulted in conduction abnormalities in whole adult rabbit hearts and induced a reduction in the peak slow inward current in patch-clamp experiments of isolated rabbit ventricular myocytes, suggesting involvement of calcium channels. Clinical investigations are moving away from case reports, and recent studies now include substantial entries. Assuming that patients reported from the United States, Finland, and England are all separate, sera from at least 100 different mothers of infants with congenital heart block have been studied. Although there is apparently no serologic profile that is unique to mothers of affected children, compared with mothers of healthy children, anti-Ro/SS-A antibodies (anti-52-kD antibodies are more prevalent by immunoblot in congenital heart block, although all these sera are likely to have anti-60-kD antibodies by immunoprecipitation) are usually of high titer and associated with anti-La/SS-B antibodies. To date, the only maternal autoantibodies that have been associated with congenital heart block recognize Ro/SS-A or La/SS-B antigens. Mothers of affected infants are often asymptomatic, and when symptomatic, the clinical features are frequently characteristic of Sjögren's syndrome. Although treatment of affected fetuses with dexamethasone has successfully diminished associated effusions, there has been no report of reversal of established third-degree heart block.