Family link between autoimmune disease and congenital heart block

Increased risk of autoimmune disease in people with congenital heart block is shared by their siblings.

Complete congenital heart block without an associated malformation of the heart is a rare condition, affecting only 1 in every 23,000 births in the general population. People with congenital heart block are more likely to get cardiovascular diseases, such as heart failure, heart disease or stroke.

The condition is more common in the children of women with so called Ro/SSA autoantibodies in their blood. An antibody is a protein that the immune system produces to protect against infectious agents, such as viruses or bacteria. In autoimmune disease, the body makes antibodies that attack its own tissues. Women with these autoantibodies often have autoimmune diseases such as  systemic lupus erythematous (usually shortened to SLE or Lupus) or Sjögren’s syndrome, but may also be without symptoms of a rheumatic disease. During pregnancy, the autoantibodies cross the placenta, which may result in damage to the baby’s heart. It is thought that around 1–2% of babies conceived by mothers with these types of autoantibodies will develop a congenital heart block.

What did the authors hope to find?
The authors wanted to look at the spectrum of disease in people with congenital heart block, and how it affects them over the short- and long term. They also wanted to see whether the brothers and sisters of people with congenital heart block showed any signs of disease.

Who was studied?
The study looked at families where women with anti-Ro/SSA autoantibodies had given birth to at least one child with a congenital heart block. The authors included 119 people with congenital heart block, and their brothers and sisters (siblings). The siblings had to be full siblings, which means that they have both the same mother and father as the person with congenital heart block. Full siblings have similar genetic makeup, and would have been exposed to the same autoantibodies from their mother while they were in her womb.

How was the study conducted?
This was a retrospective observational study, which means that the authors used existing databases of patient records to look back and find people for each group. There was no interventional treatment given as part of this study.

By using the nationwide patient register in Sweden, which contains data on diagnoses assigned to all residents in Sweden, the authors were able to look at the frequency of diseases in people with congenital heart block and their siblings, and compare these to the general population. Thus, they were able to identify diseases more (or less) likely to occur in people with congenital heart block or in their siblings.

What were the main findings of the study?
People with congenital heart block can have many other health problems, including cardiovascular disease, infections, chronic inflammatory conditions and autoimmune diseases. People born to women with anti-Ro/SSA autoantibodies – and who had a brother or sister with congenital heart block – were themselves at a risk higher than the general population of having an autoimmune disease.

Are these findings new?
Some previous research and case reports have reported autoimmune disease, neurological conditions and cardiovascular complications in people with congenital heart block. However, according to the authors, no previous study has systematically assessed the spectrum of linked conditions and diseases in this group of people and their siblings.

What are the limitations of the study?
Because congenital heart block is a relatively rare condition, the size of the study was limited. Also, although the average follow-up time was 17 years, a longer observation period may have provided more insights about how congenital heart block affects people over the course of their life.

What do the authors plan on doing with this information?
Additional studies are underway to see whether there are interventions or treatments that could help people with congenital heart block.

What does this mean for me?
If you have congenital heart block, you have a higher risk of developing autoimmune diseases than other people. This risk might also be higher for members of your immediate family, even if they do not have congenital heart block. These results suggest that you – and also potentially your brothers and sisters – might benefit from monitoring to help you stay well.

If you have any concerns about your disease, you should talk to your doctor.

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Date prepared: May 2019
Summary based on research article published on: 26 February 2019
From: Mofors J, et al. Comorbidity and long-term outcome in patients with congenital heart block and their siblings exposed to Ro/SSA autoantibodies in utero. Ann Rheum Dis 2019;78:696–703. doi:10.1136/ annrheumdis-2018-214406

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