Clinical and pathologic implications of extending the spectrum of maternal autoantibodies reactive with ribonucleoproteins associated with cutaneous and now cardiac neonatal lupus from SSA/Ro and SSB/La to U1RNP

- Heart block in the absence of structural abnormalities is associated with autoantibodies against SSA/Ro and/or SSB/La in greater than 85% of cases.
- Cutaneous manifestations of neonatal lupus have been reported with anti-U1RNP.
- This is the first case report of heart block associated with anti-U1RNP antibodies absent the traditionally associated neonatal lupus antibodies.
- Testing for anti-U1RNP should be considered in heart block cases in which neonatal lupus antibodies are negative and there is no structural etiology.

While the relationship between maternal connective tissue diseases and neonatal rashes was described in the 1960s and congenital heart block in the 1970s, the “culprit” antibody reactivity to the SSA/Ro-SSB/La ribonucleoprotein complex was not identified until the 1980s. However, studies have shown that approximately 10-15% of cases of congenital heart block are not exposed to anti-SSA/Ro-SSB/La. Whether those cases represent a different disease entity or whether another antibody is associated has yet to be determined. Moreover, the cutaneous manifestations of neonatal lupus have also been identified in infants exposed only to anti-U1RNP antibodies. In this review, we describe what we believe to be the first case of congenital heart block exposed to maternal anti-U1RNP antibodies absent anti-SSA/Ro-SSB/La. The clinical and pathologic characteristics of this fetus are compared to those typically seen associated with SSA/Ro and SSB/La. Current guidelines for fetal surveillance are reviewed and the potential impact conferred by this case is evaluated.