NL is an autoimmune condition acquired passively by the newborn from mothers with anti-Ro/SS-A and anti-La/SS-B antibodies. Anti-SSA antibodies target the antigenic subunit of molecular weight 52kD or 60kD, known as anti-Ro52 and anti-Ro60, respectively. The former is more commonly found in cases of cardiac manifestations. Cardiac NL rarely occurs in offspring of women exclusively positive for anti-La/SS-B[
61]. However, when both anti-Ro/SS-A and anti-La/SS-B antibodies are present, the likelihood of NL increases[
62]. Buyon J. in 1993[
63]and Jaeggi E. in 2010[
64] showed that the lower the antibody titer, the lower the risk of newborn lupus. Overall, 40% of SLE patients have these antibodies, which are also found in other rheumatological conditions such as Sjogren's syndrome, undifferentiated connective tissue diseases[
65], rheumatoid arthritis, as well as in the general population[
66]. Notably, 50% of mothers of infants born with NL will develop the autoimmune disease after pregnancy[
67]. Cutaneous manifestations of NL have also been identified in offspring of mothers who have only anti-U1RNP antibodies[
68]. The precise pathogenetic mechanism of NL remains elusive. A cross-reaction between maternal autoantibodies and various embryonic tissues has been hypothesized. In fact, being IgG, mother's autoantibodies are able to cross the placenta from the second trimester. In
vitro studies have demonstrated that anti-Ro/SS-A and anti-La/SS-B bind calcium-regulating molecules such as calcium channels T and L, which are present in cardiac conduction tissue. This binding would likely promote a local inflammatory response, leading to tissue damage. However, only 2% of offspring born to mothers carrying anti-SSA and anti-SSB antibodies develop manifestations of NL. Probably a genetic predisposition promotes progression to fibrosis or disrupts the inflammatory process. Some studies have indicated an increase in biomarkers of inflammation and cardiac distress (C reactive protein, metalloproteinases, NT-ProBNP) in the umbilical cord blood of neonates with cardiac manifestations compared to those without such manifestations[
69]. A type of macrophage expresses high levels of sialic acid-binding Ig-like lecithin 1 (SIGLEC-1). It is a pro-inflammatory cell, upregulated by type I interferon (IFN). These macrophages were found in the cardiac tissue of fetuses with CHB[
70]. A study conducted by Lisney et al. demonstrated a correlation where mothers of children with congenital heart block (CHB) exhibited significantly higher expression levels of SIGLEC-1 and IFN-α compared to mothers with healthy children[
71]. The term "neonatal lupus" refers to a range of manifestations that can vary both in severity and duration. These manifestations include transient skin involvement, characterized by the appearance of annular erythematous lesions. Manifestations typically affect face, scalp and neck. These lesions may be present from birth or emerge between 4 and 6 weeks of life, usually auto-resolving in 17 weeks, when mother’s autoantibodies disappear from neonatal blood. Additionally, there may be transient and asymptomatic liver involvement, marked by a mild elevation of transaminases, as well as mild hepatosplenomegaly that can progress to cholestasis and hepatitis. Varying degrees of cytopenia can occur, occasionally progressing to aplastic anemia. Neurological involvement, often transient, may present with subtle symptoms and nonspecific neuroradiological signs, or with macrocephaly and hydrocephalus. However, the association with NL is not universally supported by all researchers. The most severe complication, but also the least frequent, involves cardiac involvement [
68]. Cardiac NL occurs between 18
th and 26
th GW, corresponding to the embryonic development period of cardiac tissue. About 2% of the newborns from mothers with anti-Ro/SS-A and anti-La/SS-B antibodies develop cardiac NL. The recurrence risk of cardiac NL in a subsequent pregnancy is 12-17%, whereas if the woman has already given birth to a child with non-cardiac NL manifestations, the likelihood is similar to that of patients with only anti-SSA and anti-SSB. Typically, it manifests without structural cardiac anomalies but with rhythm disturbances, notably atrioventricular congenital heart block (CHB) of first, second, or third degree (Complete CHB, CCHB). In the latter case, mortality reaches 17% by the 30
th GW. Other potential cardiac complications include endocardial fibroelastosis and consequent dilatated cardiomyopathy, congestive heart failure, sinus bradycardia, valvular alterations, and myocarditis. Current recommendations suggest a close echocardiographic monitoring of the fetal heartbeat between 18
th and 26
th GW. However, some studies[
72] are questioning the usefulness of this approach, since only rarely standard fetal heart rate surveillance has detected CHB in time for effective treatment. Evers
et al. [
73], suggested that utilizing antibody levels to categorize this population can enhance surveillance for CHB. Standard (weekly) screening is not cost-effective and leads to excessive resource utilization.
In the past, it was evenly recommended the administration of fluorinated GC, such as dexamethasone and betamethasone. The rationale for their use was based on the idea that, by crossing the placenta, they could act on the inflammatory component of cardiac damage. However, multiple studies[
74,
75] show that first-degree block does not worsen in fetuses of untreated mothers. Second-degree BAVs tend to regress or progress whether treated or untreated, whereas third-degree blocks never regress with steroid therapy[
75]. A metanalysis of 9 studies, conducted by Hoxha et.al, analyzed 747 pregnancies in which fluorinated steroids do not demonstrate superiority over other treatments for patients with CHB
72. In this study the outcomes were: live birth, prevention of incomplete CHB progression, pacemaker implantation, and extra-nodal disease.
Thus, whereas of minimal benefits, GC can lead to a series of both fetal and maternal complications, including infections, osteoporosis, osteonecrosis, diabetes, IUGR, and oligohydramnios. It has also been noted that their preventive use has no impact on NL development. There have been no controlled studies assessing the effectiveness of plasmapheresis in cardiac NL. IVIG was not demonstrated to prevent cardiac NL at a dose of 400 mg/kg.[
76] In contrast, several studies[
77,
78,
79] have demonstrated that the use of HCQ from the early GW reduces the risk of NL, even in cases of NL in previous pregnancies. Considering the potential benefits, HCQ should be initiated before conception or as early as possible during the first trimester in women positive for anti-SSA/-SSB antibodies, particularly in those with a history of CHB. With no therapies proven effective for occurred CHB, close monitoring is recommended. In cases of fetal distress, early delivery is indicated. It has also been observed that 2% of AV blocks may appear up to 1 month after birth; hence, these children should be monitored by an expert pediatrician in the early weeks of life. The only procedure that increases the survival of these infants is the implantation of a pacemaker. Indeed, 70% have undergone pacing by the age of 10 years[
76].