Neonatal lupus erythematosus: a transplacentally acquired autoimmune disorder

Auxilin is a novel susceptibility gene for congenital heart block which directly impacts fetal heart function

OBJECTIVE

Neonatal lupus erythematosus (NLE) may develop after transplacental transfer of maternal autoantibodies with cardiac manifestations (congenital heart block, CHB) including atrioventricular block, atrial and ventricular arrhythmias, and cardiomyopathies. The association with anti-Ro/SSA antibodies is well established, but a recurrence rate of only 12%-16% despite persisting maternal autoantibodies suggests that additional factors are required for CHB development. Here, we identify fetal genetic variants conferring risk of CHB and elucidate their effects on cardiac function.

METHODS

A genome-wide association study was performed in families with at least one case of CHB. Gene expression was analysed by microarrays, RNA sequencing and PCR and protein expression by western blot, immunohistochemistry, immunofluorescence and flow cytometry. Calcium regulation and connectivity were analysed in primary cardiomyocytes and cells induced from pleuripotent stem cells. Fetal heart performance was analysed by Doppler/echocardiography.

RESULTS

We identified DNAJC6 as a novel fetal susceptibility gene, with decreased cardiac expression of DNAJC6 associated with the disease risk genotype. We further demonstrate that fetal cardiomyocytes deficient in auxilin, the protein encoded by DNAJC6, have abnormal connectivity and Ca²⁺ homoeostasis in culture, as well as decreased cell surface expression of the Ca_v1.3 calcium channel. Doppler echocardiography of auxilin-deficient fetal mice revealed cardiac NLE abnormalities in utero, including abnormal heart rhythm with atrial and ventricular ectopias, as well as a prolonged atrioventricular time intervals.

CONCLUSIONS

Our study identifies auxilin as the first genetic susceptibility factor in NLE modulating cardiac function, opening new avenues for the development of screening and therapeutic strategies in CHB.

Environmental and lifestyle factors influencing risk of congenital heart block during pregnancy in anti-Ro/SSA-positive women

OBJECTIVES

Congenital heart block (CHB) occurs in 1%-2% of anti-Ro/SSA antibody-positive pregnancies. A population-based recurrence rate of 12% indicates that factors other than maternal autoantibodies influence CHB development. Here we report the first investigation to identify environmental and lifestyle factors influencing the risk of CHB.

METHODS

A questionnaire focused on environmental and lifestyle factors was distributed to anti-Ro/SSA antibody-positive women who had given birth to at least one child with CHB, and additional data were retrieved from national health registers. Statistical analysis was performed comparing pregnancies resulting in a child with CHB (n=81) and pregnancies resulting in unaffected siblings (n=108).

RESULTS

Analysis of maternal body mass index and weight gain during pregnancy as well as medication intake and sun exposure did not reveal significant differences between CHB-affected and non-CHB pregnancies. By contrast, we found that reports of infections and stressful events were significantly more frequent in CHB-affected pregnancies than in non-CHB affected pregnancies (OR 17.9, 95% CI 4.1 to 162.8, p<0.001 and OR 5.5, 95% CI 1.1 to 55.1, p<0.05, respectively). Notably, outdoor activity a few hours per day emerged as a protective factor (OR 0.52, 95% CI 0.27 to 0.99, p<0.05). The previously reported factor seasonal timing of pregnancy was confirmed (OR 2.2, 95% CI 1.1 to 4.2, p<0.05), and multivariate analysis revealed that this association was partly explained by infection and outdoor activity.

CONCLUSIONS

In this retrospective study, infections, stressful events and time spent with outdoor activities emerged as potential environmental and lifestyle factors influencing the risk of CHB, warranting confirmation in prospective studies.

Neonatal lupus erythematosus: a report of four cases

Neonatal lupus erythematosus is a very rare disease, clinically characterized by skin lesions that resemble those of subacute or discoid lupus erythematosus and/or congenital heart block. Generally, when patients have skin manifestations, they have no cardiac defects and vice-versa; however, in 10% of cases these manifestations may coexist. Other findings may include hematologic, hepatic and neurological abnormalities. This condition is caused by the transplacental passage of maternal autoantibodies against Ro (95%), La and, less frequently, U1-ribonucleoprotein (U1-RNP). The present case report describes four patients with clinical, histopathological and immunological findings compatible with neonatal lupus erythematosus, their treatment and progress.

Neonatal lupus erythematosus

Neonatal lupus Erythematosus (NLE) is a disorder characterized by maternal autoantibodies against RNA protein complex, Ro/SSA or SSB/La. These maternal IgG antibodies cross the placenta and potentially lead to fetal tissue damage and the clinical manifestations NLE. NLE is uncommon, affects females more than males, has no race predilection, and involves multiple organs. It has cutaneous manifestations similar to subacute cutaneous lupus erythematosus (SCLE). In addition to skin findings, patients with NLE have a significant risk of congenital heart block (CHB), a potentially fatal complication. Less frequently, hematologic and hepatic abnormalities occur. Approximately half of the reported cases have skin disease and half have CHB. Approximately 10% have both CHB and skin findings. The cutaneous, hematologic, and hepatic abnormalities are transient, clearing by 6 months of age. However, CHB is permanent and requires a pacemaker in many cases. The disorder results from the passive transfer of maternal autoantibodies, anti-RoSSA and anti-La/SSB. Sontheimer and McCauliffe reviewed the pathogenic role of anti-Ro antibody in NLE lesions and summarize evidence supporting its pathogenic role. Additional evidence suggests the possibility that Ro-antigen-specific T-cells may be present in SCLE patients and have the capacity to cause direct injury to the skin. McCuistion and Schoch first suggested this hypothesis in 1954 when they described an infant with LE skin findings born to a mother with systemic lupus erythematosus (SLE). Since this initial observation, a number of researchers have documented the role of maternal autoantibodies in the pathogenesis of this disorder. The true incidence of NLE is not known; however, it is known that NLE accounts for approximately 80% of all cases of CHB, and the incidence of CHB is 1 per 20,000 live births. Therefore, it can be assumed that the incidence of NLE is at least 1 per 12,500 live births.

A serologic marker for fetal risk of congenital heart block

OBJECTIVE

To analyze the humoral immune response to Ro/SSA and La/SSB antigens in detail, in order to identify markers in mothers at high risk of having children with congenital heart block (CHB).

METHODS

Serum samples were obtained from 9 Ro/La-positive mothers who gave birth to affected children, from their 8 newborns with CHB, and from 26 Ro/La-positive mothers whose children were healthy. Antibodies against Ro 52-kd, Ro 60-kd, and La were analyzed by enzyme-linked immunosorbent assay and immunoblotting, using recombinant proteins and synthetic peptides.

RESULTS

IgG anti-Ro 52-kd antibodies were detected in all mothers who gave birth to children with CHB, as well as in their affected children, but were less frequent and at lower levels in control mothers. Fine mapping revealed a striking difference in which the response in mothers with affected children was dominated by antibodies to amino acids 200-239 of the Ro 52-kd protein (P = 0.0002), whereas the primary activity in control mothers was against amino acids 176-196 (P = 0.001). Furthermore, 8 of 9 mothers of children with CHB had antibody reactivity against amino acids 1-135 of the Ro 52-kd protein, containing 2 putative zinc fingers reconstituted under reducing conditions.

CONCLUSION

The results suggest that development of CHB is strongly dependent on a specific antibody profile to Ro 52-kd, which may be a useful tool to identify pregnant Ro/La-positive women at risk of delivering a baby with CHB. Close monitoring of mothers at high risk would enable early detection of a block that is still developing and allow early treatment to combat more serious complications.

Maternal issues affecting the fetus

Maternal disorders and exposures that affect fetal cardiac structure and function are reviewed, emphasizing fetal echocardiographic diagnosis and monitoring, and approaches for in utero therapy. Maternal diabetes, hyperthyroidism, lupus erythematosis, epilepsy, congenital heart disease, infections, and drug exposures are considered.

The health of mothers of children with cutaneous neonatal lupus erythematosus differs from that of mothers of children with congenital heart block

PURPOSE

Neonatal lupus erythematosus is caused by the transplacental passage of maternal autoantibodies. The aim of this study was to determine the risk of connective tissue disorders in mothers of children with cutaneous neonatal lupus erythematosus, as compared with the risk in mothers of children with congenital heart block, which is also often caused by maternal autoantibodies.

SUBJECTS AND METHODS

We prospectively studied all mothers of children with cutaneous neonatal lupus erythematosus during a 14-year period at the Hospital for Sick Children, Toronto, Ontario, Canada. We identified 28 mothers, of whom 24 were eligible for study. The health and antibody status of the mothers were determined at the birth of the child and at followup.

RESULTS

All mothers had anti-Ro antibodies at the time of birth. Initially 10 mothers were healthy and 14 mothers had either a defined (n = 9) or an undifferentiated (n = 5) autoimmune disorder. At a mean follow-up of 7 years, 13 (1 of whom had died) had a defined connective tissue disease, and 5 had an undifferentiated autoimmune disorder. Only 6 (25%) remained asymptomatic. By comparison, 36 (56%) of 64 mothers of children with congenital heart block were asymptomatic at follow-up (P <0.005).

CONCLUSIONS

The majority of mothers of children with cutaneous neonatal lupus erythematosus had a defined or undifferentiated autoimmune disorder at the time of the child's birth, and others developed these conditions during follow-up. The health of these mothers appears to differ from that of mothers of children with congenital heart block.

Chondrodysplasia punctata stemming from maternal lupus erythematosus

The finding of stippled epiphyses on a neonatal radiograph generates a wide differential diagnosis, including genetic and teratogenic causes. We report the case of a male infant with stippled epiphyses evident on neonatal radiographs in whom a typical rash of lupus erythematosus developed. The skin abnormalities in the infant resulted in a diagnosis of systemic lupus erythematosus in his mother. Over a 3-year follow-up period, the child has demonstrated strikingly short stature, midface hypoplasia, anomalous digital development, slow resolution of the stippled epiphyses, and near normal cognitive development. The differential diagnosis of chondrodysplasia punctata and the literature supporting maternal lupus as one cause are reviewed.

Systemic lupus erythematosus: perinatal and neonatal implications

Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder that can affect almost all organ systems in the body. It is most common in women of childbearing age and may cause multiple peripartum complications. This article reviews the pathophysiology of SLE and the effects of SLE on fertility and pregnancy. The complexities of managing a pregnant patient with SLE are reviewed, and the importance of interdisciplinary collaboration discussed, as well as the effects of SLE on the fetus and a review of neonatal lupus erythematosus. Finally, a case report of a pregnant patient with SLE with challenging clinical management issues is presented.

Management of collagen vascular diseases in childhood

Collagen vascular diseases seen in children include systemic, discoid and neonatal lupus, dermatomyositis, scleroderma, juvenile rheumatoid arthritis, and, in rare cases, Sjogren's syndrome. Although these diseases are uncommon in children, when seen, they are associated with significant morbidity. This review describes the clinical features of each condition and provides an overview of treatment options now available. These include numerous systemic treatments which can be used as steroid-sparing agents.

Neonatal lupus erythematosus: analysis of HLA class II alleles in mothers and siblings from seven Japanese families

BACKGROUND

Neonatal lupus erythematosus (NLE) is a syndrome characterized by dermatitis and congenital heart block. The disease is mostly associated with transplacental passage of maternal anti-Ro(SS-A) or anti-La(SS-B) antibodies. Maternal HLA-DR3 and DQ2 alleles are associated with NLE in white and North American black populations.

OBJECTIVE

We sought evidence of a potential genetic disposition to NLE in mothers with a relatively homogeneous ethnic background.

METHODS

Class II human major histocompatibility complex HLA-DRB1, DQA1, DQB1, and DPB1 alleles were determined by polymerase chain reaction-restriction fragment length polymorphism in anti-Ro(SS-A)-positive mothers as well as in infants from seven Japanese families with siblings concordant or discordant for disease expression of NLE.

RESULTS

All seven mothers had two or three DQ alleles of DQA1 and DQB1 possessing specific amino acid residues, which are reportedly associated with anti-Ro(SS-A) autoantibody response in white and black populations. There was no class II HLA profile that distinguished disease manifestations of NLE in infants.

CONCLUSION

The HLA class II allele associations with anti-Ro(SS-A) autoantibodies that have been noted in other ethnic groups were also found in Japanese anti-Ro(SS-A)-positive mothers whose infants had NLE, suggesting shared susceptibility factors across racial barriers in maternal predisposition to Ro(SS-A) autoimmune response.

Disparate locations of the 52- and 60-kDa Ro/SS-A antigens in cultured human keratinocytes

Anti-52- and anti-60-kDa Ro/SS-A (Ro) autoantibodies are produced by most patients with subacute cutaneous lupus erythematosus and neonatal lupus erythematosus and are thought to be pathogenic in these two disorders. To learn more about the epidermal antigens targeted by Ro autoantibodies, a panel of anti-52 and anti-60-kDa Ro antibodies was purified from human autoimmune sera and rabbit antisera and then used to: (i) determine the expression and location of the Ro antigens in human keratinocytes; (ii) clarify discrepancies in previous localization studies; and (iii) verify the existence of Ro autoantibodies that cross-react with the 52- and 60-kDa Ro antigens, as previously reported. By immunoblot analysis these antibodies demonstrate that 52- and 60-kDa Ro proteins are expressed in normal human skin and cultured keratinocytes. By indirect immunofluorescence studies with cultured human cells, the anti-52-kDa Ro antibodies produce fine granular cytoplasmic fluorescence and less intense nuclear fluorescence, with apparent nucleolar sparing. The anti-60-kDa Ro autoantibodies produce weak cytoplasmic fluorescence and intense coarse granular nuclear fluorescence with apparent nucleolar sparing. We found distinct differences in the intracellular localization of the 52- and 60-kDa Ro autoantigens. This difference suggests that the 52-and 60-kDa Ro antigens may have independent cellular functions. Finding 60-kDa Ro antigen predominantly in the nucleus challenges the notion that the majority of the intracellular 60-kDa Ro antigen is complexed with the cytoplasmic hY RNA. Additionally, our failure to find a cross-reactive epitope on these two proteins indicates that the 52-kDa Ro antigen is probably a true immunogen and not merely a protein that cross-reacts with anti-60-kDa Ro autoantibodies, as others have suggested.