Neonatal lupus syndromes

Abstract

The neonatal lupus syndromes (NLS), while quite rare, carry significant mortality and morbidity in cases of cardiac manifestations. Although anti-SSA/Ro-SSB/La antibodies are detected in .85% of mothers whose fetuses are identified with congenital heart block (CHB) in a structurally normal heart, when clinicians applied this testing to their pregnant patients, the risk for a woman with the candidate antibodies to have a child with CHB was at or below 1 in 50. While the precise pathogenic mechanism of antibody-mediated injury remains unknown, it is clear that the antibodies alone are insufficient to cause disease and fetal factors are likely contributory. In vivo and in vitro evidence supports a pathologic cascade involving apoptosis of cardiocytes, surface translocation of Ro and La antigens, binding of maternal autoantibodies, secretion of profibrosing factors (e.g., TGFb) from the scavenging macrophages and modulation of cardiac fibroblasts to a myofibroflast scarring phenotype. The spectrum of cardiac abnormalities continues to expand, with varying degrees of block identified in utero and reports of late onset cardiomyopathy (some of which display endocardial fibroelastosis). Moreover, there is now clear documentation that incomplete blocks (including those improving in utero with dexamethasone) can progress postnatally, despite the clearance of the maternal antibodies from the neonatal circulation. Better echocardiographic measurements which identify first degree block in utero may be the optimal means of approaching pregnant women at risk. Prophylactic therapies, including treatment with intravenous immunoglobulin, await larger trials. In order to achieve advances at both the bench and bedside, national research registries established in the US and Canada are critical.