[Neonatal lupus erythematosus as an example of passively acquired autoimmunity]

Neonatal lupus erythematosus is a typical example of passively acquired autoimmune disease. Congenital heart block is the main complication caused by transplacentally transferred maternal IgG antibodies directed against SS-A- or SS-B-antigen. While the transient lupus dermatitis occurs post partum and is often triggered by UV-light exposition, the irreversible cardial damage takes place between the 18. and 24, week of pregnancy. During this period 52-kD-SS-A- and 48-kD-SS-B-antigen are expressed in the fetal cardial tissue. The autoimmune reaction leads to an irreversible fibrotic destruction of the atrioventricular node. The resulting AV block and an antibody-induced perimyocarditis support the development of fetal bradyarrhythmia and hydrops. The very early diagnosis of a fetal heart block in bradycardiac fetus by echocardiography is essential for a consecutive therapy with steroids. By a reduction of the maternal antibodies an improvement of cardial symptoms in the fetus may be achieved in cases with fetal hydrops. Pregnant women at high risk with known connective tissue disease, previous children with congenital heart block, high titers of SS-A-/SS-B-antibodies and immunogenetic predisposition (HLA-DR3) have to be monitored intensively because of the possibility of a prophylaxis with dexamethasone and, in some selected cases, plasmapheresis.