Immunology of pregnancy and reproductive health in autoimmune rheumatic diseases. Update from the 11th International Conference on Reproduction, Pregnancy and Rheumatic Diseases.

Autoimmune rheumatic diseases (ARD) can affect women and men during fertile age, therefore reproductive health is a priority issue in rheumatology. Many topics need to be considered during preconception counselling: fertility, the impact of disease-related factors on pregnancy outcomes, the influence of pregnancy on disease activity, the compatibility of medications with pregnancy and breastfeeding. Risk stratification and individualized treatment approach elaborated by a multidisciplinary team minimize the risk of adverse pregnancy outcomes (APO). Research has been focused on identifying biomarkers that can be predictive of APO. Specifically, preeclampsia and hypertensive disorders of pregnancy tend to develop more frequently in women with ARD. Placental insufficiency can lead to intrauterine growth restriction and small-for-gestational age newborns. Such APO have been shown to be associated with maternal disease activity in different ARD. Therefore, a key message to be addressed to the woman wishing for a pregnancy and to her family is that treatment with compatible drugs is the best way to ensure maternal and fetal wellbeing. An increasing number of medications have entered the management of ARD, but data about their use in pregnancy and lactation are scarce. More information is needed for most biologic drugs and their biosimilars, and for the so-called small molecules, while there is sufficient evidence to recommend the use of TNF inhibitors if needed for keeping maternal disease under control. Other issues related to the reproductive journey have emerged as "unmet needs", such as sexual dysfunction, contraception, medically assisted reproduction techniques, long-term outcome of children, and they will be addressed in this review paper. Collaborative research has been instrumental to reach current knowledge and the future will bring novel insights thanks to pregnancy registries and prospective studies that have been established in several Countries and to their joint efforts in merging data.

Anti-SSA/Ro positivity and congenital heart block: obstetric and foetal outcome in a cohort of anti-SSA/Ro positive pregnant patients with and without autoimmune diseases.

OBJECTIVES: Neonatal lupus (NL) is an acquired disease caused by the transplacental passage of anti-SSA/Ro antibodies. The rate of congenital heart block (CHB), its most serious manifestation, ranges from 1 to 5%. The aim of this study was to retrospectively assess the prevalence of CHB in anti-SSA/Ro positive pregnant women with or without systemic autoimmune diseases from 2010 to 2020. METHODS: Patients underwent monthly visit and a shared follow-up programme of weekly (16th-24th week) foetal heart rate assessment by obstetric ultrasound. RESULTS: 322 pregnancies in 258 anti-SSA/Ro patients were included; 314 were followed from the beginning of pregnancy because of the known presence of anti-SSA/Ro autoantibodies and 1 case of CHB occurred in an anti-SSA/Ro+ asymptomatic subject (0.3%). In the same period, 8 additional patients were referred to our clinics after in utero CHB diagnosis and subsequent discovery of anti-SSA/Ro without a disease diagnosis. Globally, 9 cases of congenital CHB (2.8%) occurred: 7 complete, 1 II-III degree and 1 rst degree CHB. Anti-SSB/La positivity was associated with a higher risk of CHB (7.8% vs. 1.2%; p=0.0071). No differences in maternal or foetal outcomes were found in comparison with a large cohort of unselected pregnancies except for caesarian section. Hydroxychloroquine (HCQ) was used in 58.3% pregnancies, with a different prevalence according with maternal diagnosis. CONCLUSIONS: Our data suggest that anti-SSA/Ro positive patents with a de ned systemic autoimmune disease undergoing a strict follow-up since positive pregnancy test display a low risk of pregnancy complications, including but not limited to NL.

Clinical Delphi on aPL Negativization: Report from the APS Study Group of the Italian Society for Rheumatology (SIR-APS).

BACKGROUND: The rate of antiphospholipid antibody (aPL) negativization in antiphospholipid syndrome (APS) patients is uncertain, but it is estimated to be as high as 8%. Currently, a consensus definition of aPL negativization is lacking, as well as international recommendations on how to approach treatment in patients with a persistent aPL-negative seroconversion. AIM: The aim of the Delphi survey was to evaluate the clinical approach and level of consensus among experts from the APS Study Group of the Italian Society for Rheumatology (SIR-APS) in different clinical scenarios. METHODS: Experts of SIR-APS were contacted using a survey methodology. RESULTS: A structured survey was circulated among 30 experts. Up to 90% of the interviewed experts agreed on defining aPL negativization as the presence of two negative determinations, 1 year apart (90%). Almost full consensus exists among experts in some clinical settings, including: (1) the role of aPL negativization in the management of a thrombotic event determined by concomitant presence of cardiovascular risk factors, both modifiable and not modifiable (90%); (2) approach to young patients with triple aPL positivity who experienced pulmonary arterial thrombotic events and tested negative for aPL detection after 5 years of vitamin K antagonist (VKA) treatment (90%); (3) the use of "extra criteria" aPL antibody testing before pondering VKA suspension (93%). CONCLUSION: A substantial agreement exists among experts on how to define aPL negativization. VKA suspension should be embraced with extreme caution, particularly in case of previous thrombotic events and/or triple aPL positivity. Nevertheless, VKA cessation might be considered when risk factors are carefully monitored/treated and the presence of "extra criteria" aPL is ruled out.

Long-term Outcome of Children Born to Women with Autoimmune Rheumatic Diseases: A Multicentre, Nationwide Study on 299 Randomly Selected Individuals.

The concern about the offspring's health is one of the reasons for a reduced family size of women with rheumatic diseases (RD). Increased risk of autoimmune diseases (AD) and neurodevelopmental disorders (ND) has been reported in children born to patients with RD. Within a nationwide survey about reproductive issues of women with RD, we aimed at exploring the long-term outcome of their children. By surveying 398 patients who received their diagnosis of RD during childbearing age (before the age of 45), information about the offspring were obtained from 230 women who declared to have had children. A total of 148 (64.3%) patients were affected by connective tissue diseases (CTD) and 82 (35.7%) by chronic arthritis. Data on 299 children (156 males, 52.1%; mean age at the time of interview 17.1 ± 9.7 years) were collected. Twelve children (4.0%), who were born to patients with CTD in 75% of the cases, were affected by AD (8 cases of celiac disease). Eleven children had a certified diagnosis of ND (3.6%; 6 cases of learning disabilities); 9 of them were born to mothers with CTD (5 after maternal diagnosis). No association was found between ND and prenatal exposure to either maternal autoantibodies or anti-rheumatic drugs. Absolute numbers of offspring affected by AD and ND were low in a multicentre cohort of Italian women with RD. This information can be helpful for the counselling about reproductive issues, as the health outcomes of the offspring might not be an issue which discourage women with RD from having children.

Improved Pregnancy Outcome in Patients With Rheumatoid Arthritis Who Followed an Ideal Clinical Pathway.

OBJECTIVE: To assess the effect of optimal management of pregnancy on a composite outcome of miscarriage and complicated birth among women with rheumatoid arthritis (RA). METHODS: Data were extracted from health care databases of the Lombardy Region, Italy (2004-2013) as a part of the Record-Linkage on Rheumatic Diseases Study. Analyses included women with RA identified through a copayment exemption code (International Classification of Diseases, Ninth Revision, Clinical Modification code 714.0) and controls from the general population, ages 18-50 years. Seven health care quality indicators (HCQI) were constructed and summarized in 3 pathway indicators: diagnostic, therapeutic, and prenatal follow-up. Complicated birth or miscarriage were used to identify the adverse pregnancy outcome (APO). The relationship between HCQI and APO was analyzed using logistic models, and the results were presented as odds ratios (ORs) and 95% confidence intervals (95% CIs). RESULTS: Data from the study cohort included the first pregnancy observed in 443 patients with RA compared with 6,097 women belonging to the general population. In the RA population, patients who followed the 3 pathway indicators had a reduced risk of overall APO, with an OR of 0.60 (95% CI 0.39-0.94), and reduced risk of miscarriage/perinatal death, with an OR of 0.40 (95% CI 0.24-0.69), compared to those who did not follow the pathway indicators. Compared with the general population, patients with RA who met all HCQI during pregnancy displayed a risk of APO with an OR of 0.92 (95% CI 0.61-1.38) and miscarriage/perinatal death with an OR of 0.77 (95% CI 0.47-1.29). CONCLUSION: The adherence to an ideal clinical pathway of pregnancy management in women with RA restored the risk of APO to that expected for the general population.

Psychosocial burden in young patients with primary anti-phospholipid syndrome: an Italian nationwide survey (The AQUEOUS study).

OBJECTIVES: The AQUEOUS (Anti-phospholipid syndrome: a QUEstionnaire for yOUng patientS) study aimed to assess how the diagnosis of primary anti-phospholipid syndrome (PAPS) affects the psychosocial status of young patients. METHODS: Subjects with PAPS aged 18-45 years were invited to compile an ad hoc designed questionnaire and the Short Form-12 to assess quality of life (QoL). RESULTS: Ninety-two patients (83.7% females) were recruited in 10 Italian centres. Vascular and obstetric manifestations were equally represented. Nearly half of the patients perceived the need for psychological support, 89.2% when considering women after pregnancy complications. Social activities and working efficiency were reduced in APS patients, also intimacy was threatened. In all cases, fatigue appeared to be the main determinant. PAPS affected family planning, due to fears of treatment side-effects, disease hereditariness, inability to care for the newborn child. Fertility appeared to be conserved: the median time to pregnancy was 2 months; assisted reproduction techniques were pursued by 5 women. Our survey documented significantly lower rates of hospitalisation and learning disabilities in 51 children born after APS diagnosis as compared to 48 children born before. PAPS patients displayed lower QoL in physical and, to a greater extent, mental scores compared to the general Italian population. Both components were significantly lower in women and in patients with fatigue. CONCLUSIONS: The AQUEOUS study assessed for the first time the unmet needs of young PAPS patients, enabling the development of a future "youth-focused" strategy to reduce disease burden.

Role of placental inflammatory mediators and growth factors in patients with rheumatic diseases with a focus on systemic sclerosis.

OBJECTIVES: Pregnancy in SSc is burdened with an increased risk of obstetric complications. Little is known about the underlying placental alterations. This study aimed to better understand pathological changes and the role of inflammation in SSc placentas. Leucocyte infiltration, inflammatory mediators and atypical chemokine receptor 2 (ACKR2) expression in SSc placentas were compared with those in other rheumatic diseases (ORD) and healthy controls (HC). METHODS: A case-control study was conducted on eight pregnant SSc patients compared with 16 patients with ORD and 16 HC matched for gestational age. Clinical data were collected. Placentas were obtained for histopathological analysis and immunohistochemistry (CD3, CD20, CD11c, CD68, ACKR2). Samples from four SSc, eight ORD and eight HC were analysed by qPCR for ACKR2 expression and by multiplex assay for cytokines, chemokines and growth factors involved in angiogenesis and inflammation. RESULTS: The number of placental CD3, CD68 and CD11 cells was significantly higher in patients affected by rheumatic diseases (SSc+ORD) compared with HC. Hepatocyte growth factor was significantly increased in the group of rheumatic diseases patients (SSc+ORD) compared with HC, while chemokine (C-C motif) ligand 5 (CCL5) was significantly higher in SSc patients compared with ORD and HC. CCL5 levels directly correlated with the number of all local inflammatory cells and higher levels were associated with histological villitis. CONCLUSIONS: Inflammatory alterations characterize placentas from rheumatic disease patients and could predispose to obstetric complications in these subjects.

Endothelial Progenitor Cell CD34+ and CD133+ Concentrations and Soluble HLA-G Concentrations During Pregnancy and in Cord Blood in Undifferentiated Connective Tissue Diseases Compared to Controls.

The objective of this study is to evaluate endothelial progenitor cells (EPCs) CD34+ CD133- and CD34+ CD133+ and soluble HLA-G (sHLA-G) concentrations among undifferentiated connective tissue disease (UCTD) subjects, compared to controls, during pregnancy and in cord blood. This is a case-control study including 29 controls and 29 UCTDs. CD34+ CD133-, CD34+ CD133+, and sHLA-G concentrations were detected in maternal plasma and in cord blood. This study was approved by the Medical-Ethical Committee of our Institution (Current Research Project N. 901-rcr2017i-23 of IRCCS Foundation Policlinico San Matteo of Pavia). Circulating CD34+ CD133- and CD34+ CD133+ counts and sHLA-G (soluble human leucocyte antigen G) concentrations in maternal peripherical blood were higher in UCTD compared to those in controls in first and third trimester of pregnancy and at delivery (p < 0.001). Maternal CD34+ CD133- and CD34+ CD133+ counts were strongly and significantly correlated in UCTD (Spearman's rho = 0.79, p < 0.0001) but not in controls (Spearman's rho = 0.10, p = 0.35). Cord blood CD34+ CD133- and CD34+ CD133+ median counts and median sHLA-G concentrations were higher among UCTD subjects than in controls (p < 0.001). Cord blood CD34+ and CD133+ counts were inversely and significantly correlated with sHLA-G concentrations among UCTDs, but not in controls. Early UCTD is characterized by increased EPC levels in maternal plasma and in cord blood and higher levels of sHLA-G, compared to controls. Data suggest that fetoplacental unit plays an independent role in the EPC response to a systemic autoimmune disease.

An observational multicentre study on the efficacy and safety of assisted reproductive technologies in women with rheumatic diseases.

OBJECTIVES: The aim was to determine whether assisted reproductive technologies (ARTs) confer additional risk in rheumatic patients (in terms of disease flare and fetal-maternal complications) and whether, if performed, their efficacy is affected by maternal disease. METHODS: Sixty infertile rheumatic women undergoing 111 ART cycles were included. Clinical pregnancy rate, live birth rate, maternal disease flares and maternal-fetal complications were recorded. RESULTS: One hundred and eleven ART cycles in 60 women were analysed. We reported 46 pregnancies (41.4%), 3 (3.1%) cases of ovarian hyperstimulation syndrome and no cases of thrombosis during stimulation, pregnancy and puerperium. One or more maternal complication was reported in 13 (30.2%) pregnancies, and fetal complications occurred in 11 fetuses (21.1%). The live birth rate was 98%, but we reported three (6%) perinatal deaths in the first days of life. During puerperium, we recorded one (2.5%) post-partum haemorrhage and one (2.5%) articular flare. CONCLUSION: The safety and efficacy of the ARTs, demonstrated in the general population, seems to be confirmed also in rheumatic patients. No evidence was found to advise against their application, and the choice of therapy should be made depending on the patient's risk profile, irrespective of whether the pregnancy is natural or artificial induced.

First Report of the Italian Registry on Immune-Mediated Congenital Heart Block (Lu.Ne Registry).

Objective: Neonatal Lupus (NL) is a rare syndrome caused by placental transfer of maternal anti-SSA/Ro and anti-La/SSB autoantibodies to the fetus. The rarity of this condition requires the establishment of multidisciplinary registries in order to improve our knowledge. Method: Inclusion criteria in this retrospective study were the maternal confirmed positivity for anti-SSA/Ro and/or anti-SSB/La antibodies, and the presence of II or III degree congenital heart block (CHB) in utero or neonatal period (up to 27 days after birth). Result: Eighty-nine cases of CHB were observed in 85 women with 88 pregnancies that occurred between 1969 and 2017. CHB was mostly detected in utero (84 cases, 94.2%), while five cases were observed in the neonatal period. A permanent pacemaker was implanted in 51 of 73 children born alive (69.8), whereas global mortality rate was 25.8% (23 cases): 16 in utero, five perinatal, and two during childhood. By univariate analysis, factors associated with fetal death were pleural effusion (p = 0.005, OR > 100; CI 95% 2.88->100 and hydrops (p = 0.003, OR = 14.09; CI 95% 2.01-122). Fluorinated steroids (FS) were administered in 71.4% pregnancies, and its use was not associated with better survival. Some centers treated all cases with fluorinated steroids and some centers did not treat any case. CHB was initially incomplete in 24 fetuses, and of them five cases of II degree block reverted to a lower degree block after treatments. Recurrence rate in subsequent pregnancies was 17.6% (3 out of 17). A prophylactic treatment was introduced in 10 of these 16 subsequent (58.8%) pregnancies, mostly with FS or high dose intravenous immunoglobulins. Conclusion: This is the first report from the Italian Registry of neonatal lupus/CHB. The live birth rate was nearly 80%, with nearly two thirds of the children requiring the implantation of a pacemaker. The management of fetuses diagnosed with CHB was heterogeneous across Italian Centers. The registry at present is mainly rheumatological, but involvement of pediatric cardiologists and gynecologists is planned.

Disease activity assessment of rheumatic diseases during pregnancy: a comprehensive review of indices used in clinical studies.

Pregnancy requires a special management in women with inflammatory rheumatic diseases (RDs), with the aim of controlling maternal disease activity and avoiding fetal complications. Despite the heterogeneous course of RDs during pregnancy, their impact on pregnancy largely relates to the extent of active inflammation at the time of conception. Therefore, accurate evaluation of disease activity is crucial for the best management of pregnant patients. Nevertheless, there are limitations in using conventional measures of disease activity in pregnancy, as some items included in these instruments can be biased by symptoms or by physiological changes related to pregnancy and the pregnancy itself may influence laboratory parameters used to assess disease activity. This article aims to summarize the current literature about the available instruments to measure disease activity during pregnancy in RDs. Systemic lupus erythematosus is the only disease with instruments that have been modified to account for several adaptations which might interfere with the attribution of signs or symptoms to disease activity during pregnancy. No modified-pregnancy indices exist for women affected by other RDs, but standard indices have been applied to pregnant patients. The current body of knowledge shows that the physiologic changes that occur during pregnancy need to be either adapted from existing instruments or developed to improve the management of pregnant women with RDs. Standardized instruments to assess disease activity during pregnancy would be helpful not only for clinical practice but also for research purposes.

"Disease knowledge index" and perspectives on reproductive issues: A nationwide study on 398 women with autoimmune rheumatic diseases.

OBJECTIVE: The reproductive choices of women affected by rheumatic diseases (RD) can be influenced by several factors, including the quality of physician-patient communication. We conducted a survey on reproductive issues aiming at exploring the unmet needs of women with RD during childbearing age. METHODS: We administered 65 multiple-choice and 12 open-answer questions about pregnancy counselling, contraception, use of drugs during pregnancy and other women reproductive issues to 477 consecutive women with RD aged 18-55 years followed-up in 24 rheumatology centres in Italy. Analysis was restricted to 398 patients who received their diagnosis of RD before the age of 45. According to the RD diagnosis, patients were subdivided into 2 groups: connective tissue diseases (n = 249) and chronic arthritis (n = 149). RESULTS: At the time of interview, women in both groups had a mean age of 40 years. Nearly one third of patients in each group declared not to have received any counselling about either pregnancy desire nor contraception. A smaller family size than desired was reported by nearly 37% of patients, because of concerns related to maternal disease in one fourth of the cases. A "Disease Knowledge Index" (DKI) was created to investigate the degree of patients' information about the implications of their RD on reproductive issues. Having received counselling was associated with higher DKI values and with a positive impact on family planning. CONCLUSION: Italian women of childbearing age affected by RD reported several unmet needs in their knowledge about reproductive issues. Strategies are needed to implement and facilitate physician-patient communication.

Antiphospholipid syndrome: state of the art on clinical practice guidelines.

Antiphospholipid syndrome (APS) is a rare disease characterised by venous and/or arterial thrombosis, pregnancy complications and the presence of specific autoantibodies called antiphospholipid antibodies. This review aims to identify existing clinical practice guidelines (CPG) as part of the ERN ReCONNET project, aimed at evaluating existing CPGs or recommendations in rare and complex diseases. Seventeen papers providing important data were identified; however, the literature search highlighted the scarceness of reliable clinical data to develop CPGs. With no formal clinical guidelines in place, diagnosis and treatment of APS is largely based on consensus and expert opinion. Patients' unmet need refers to the understanding of the disease and its clinical picture and implications, the need of education for patients, family members and healthcare providers, as well as to the development of monitoring pathways involving multiple healthcare providers.

Effect of Additional Treatments Combined with Conventional Therapies in Pregnant Patients with High-Risk Antiphospholipid Syndrome: A Multicentre Study.

The effect of additional treatments combined with conventional therapy on pregnancy outcomes was examined in high-risk primary antiphospholipid syndrome (PAPS) patients to identify the most effective treatment strategy. The study's inclusion criteria were (1) positivity to lupus anticoagulant alone or associated with anticardiolipin and/or anti-ß2 glycoprotein I antibodies; (2) a history of severe maternal-foetal complications (Group I) or a history of one or more pregnancies refractory to conventional therapy leading to unexplained foetal deaths not associated with severe maternal-foetal complications (Group II). Two different additional treatments were considered: oral-low-dose steroids (10-20 mg prednisone daily) and/or 200 to 400 mg daily doses of hydroxychloroquine and parenteral-intravenous immunoglobulins at 2 g/kg per month and/or plasma exchange. The study's primary outcomes were live birth rates and pregnancy complications. A total of 194 pregnant PAPS patients attending 20 tertiary centres were retrospectively enrolled. Hydroxychloroquine was found to be linked to a significantly higher live birth rate with respect to the other oral treatments in the Group II patients. The high (400 mg) versus low (200 mg) doses of hydroxychloroquine (p = 0.036) and its administration before versus during pregnancy (p = 0.021) were associated with a significantly higher live birth rate. Hydroxychloroquine therapy appeared particularly efficacious in the PAPS patients without previous thrombosis. Parenteral treatments were associated with a significantly higher live birth rate with respect to the oral ones (p = 0.037), particularly in the Group I patients. In conclusion, some additional treatments were found to be safe and efficacious in high-risk PAPS pregnant women.

Pregnancy in systemic sclerosis.

This comprehensive review summarizes retrospective and prospective studies on pregnancy in systemic sclerosis in order to educate physicians on critical management issues. Fertility is normal in women with established systemic sclerosis. Their rates of spontaneous losses are comparable to the general population, except for patients with late diffuse systemic sclerosis and severe internal organ involvement who may have higher risks of abortion. Prematurity is clearly higher among systemic sclerosis women, similarly to other rheumatic diseases such as systemic lupus erythematosus and anti-phospholipid antibody syndrome. A placental vasculopathy has been observed in some women with systemic sclerosis. Overall, the disease generally remains stable in most pregnancies. Women with pulmonary hypertension should avoid pregnancy on account of the high maternal mortality risk. Management of systemic sclerosis patients before and during pregnancy includes evaluation of organ involvement and autoantibody analysis, preconceptional folic acid, and discontinuation of drugs with teratogenic potential (bosentan, mycophenolate mofetil, methotrexate, etc.). Management by high-risk pregnancy teams including neonatologists is very important to ensure the best outcomes.

Undifferentiated connective tissue disease: state of the art on clinical practice guidelines.

The term 'undifferentiated connective tissue disease' (UCTD) is generally used to describe clinical entities characterised by clinical and serological manifestations of systemic autoimmune diseases but not fulfilling the criteria for defined connective tissue diseases (CTDs). In this narrative review, we summarise the results of a systematic literature research, which was performed as part of the ERN ReCONNET project, aimed at evaluating existing clinical practice guidelines (CPGs) or recommendations. No specific CPG on UCTD were found, potential areas of intervention are absence of a consensus definition of UCTD, need for specific monitoring and therapeutic protocols, stratification of UCTD based on the risk of developing a defined CTD and preventive measure for the future development of a more severe condition. Patients feel uncertainty regarding the name of the disease and feel the need of a better education and understanding of these conditions and its possible changes over time.

Association of Natural Killer Cell Ligand Polymorphism HLA-C Asn80Lys With the Development of Anti-SSA/Ro-Associated Congenital Heart Block.

OBJECTIVE: Fetal exposure to maternal anti-SSA/Ro antibodies is necessary but not sufficient for the development of autoimmune congenital heart block (CHB), suggesting that other factors, such as fetal genetic predisposition, are important. Given the previously described association between major histocompatibility complex alleles and CHB risk, we undertook the present study to test the hypothesis that a variant form of HLA-C Asn80Lys, which binds with high affinity to an inhibitory killer cell immunoglobulin-like receptor (KIR) and thus renders natural killer (NK) cells incapable of restricting inflammation, contributes to the development of CHB. METHODS: Members of 192 pedigrees in the US and Europe (194 cases of CHB, 91 unaffected siblings, 152 fathers, 167 mothers) and 1,073 out-of-study controls were genotyped on the Immunochip single-nucleotide polymorphism microarray. Imputation was used to identify associations at HLA-C Asn80Lys (Asn, C1; Lys, C2) and KIR. Tests for association were performed using logistic regression. McNemar's test and the pedigree disequilibrium test (PDT) were used for matched analyses between affected and unaffected children. RESULTS: Compared with out-of-study controls of the same sex, the C2 allele was less frequent in the mothers (odds ratio [OR] 0.63, P = 0.0014) and more frequent in the fathers (OR 1.40, P = 0.0123), yielding a significant sex-by-C2 interaction (P = 0.0002). The C2 allele was more frequent in affected siblings than in unaffected siblings (OR 3.67, P = 0.0025), which was consistent with the PDT results (P = 0.016); these results were observed in both sexes and across the US and European cohorts. There was no difference in the frequency of the inhibitory KIR genotype (KIR AA) between affected and unaffected children (P = 0.55). CONCLUSION: These data establish C2 as a novel genetic risk factor associated with CHB. This observation supports a model in which fetuses with C2 ligand expression and maternal anti-SSA/Ro positivity may have impaired NK cell surveillance, resulting in unchecked cardiac inflammation and scarring.