[Neonatal lupus: a fetal-maternal immunisation model?]

Neonatal lupus is due to passive fetal transfer of maternal anti-SSA/Ro and anti-SSB/La antibodies. The clinical spectrum includes transient skin lesions, hematologic and hepatic disorders, and neurological manifestations. Congenital heart block (CHB) is the main complication, occurring in the absence of severe cardiac malformation. The presence of anti-SSA/Ro antibodies is necessary but not sufficient to provoke CHB. The prevalence of CHB in newborns of anti-SSA/Ro-positive women ranges from 1% to 2%, and the estimated risk of recurrence is 10% to 17%. Mothers of newborns with CHB may be asymptomatic or have systemic lupus erythematosus or Sjogren's syndrome. The first pathophysiological step is the translocation of intracellular SSA/Ro-SSB/La antigens to the surface of apoptotic cardiomyocytes, where they can be bound by anti-SSA/Ro antibodies. These antibody-coated apoptotic cardiocytes are then phagocytosed by macrophages, that in turn secrete proinflammatory cytokines such as TNF and TGFbeta. This inflammatory cascade results in major alterations of the fibroblast phenotype, ultimately leading to fibrosis of the conducting system. While non-cardiac lesions are transient, CHB is permanent and is associated with significant morbidity (a pacemaker must be implanted in two-thirds of cases) and mortality (estimated at 16-19%).