We asked UK JIA Biologics Register Co-Investigator Dr Lianne Kearsley Fleet to discuss her research: Burden of comorbid conditions in children and young people with juvenile idiopathic arthritis: a collaborative analysis of 3 JIA registries , which was published in the journal Rheumatology in 2021.

What is already known?

Not much is known about what other diseases or medical conditions children and young people with arthritis (JIA) have, and how often they occur. Large international registries capture detailed information on children and young people with JIA receiving different medications, including whether or not they have or later develop other diseases. This study aimed to combine data from three large registries to look at this issue in more detail.

What was discovered?

This study included over 8000 children and young people with JIA from three different JIA registers: 2963 from the UK, 1541 from the Germany, and 3562 from an international register of 87 rheumatology centres around the world. We found that uveitis, a condition which causes inflammation in the eye, affected between 15-19% of children; however tuberculosis (TB), a serious lung infection, only affected between 0.1-1.8% of children. Chickenpox is a potentially serious infection, particularly in those taking immunosuppressive treatment such as the medicines used to treat JIA. In Germany where the chickenpox vaccine is routinely given to prevent chickenpox (over half the children had received the vaccine), we found that the levels of chickenpox infection were low, affecting only 1-in-7 children and young people. In the UK and the other countries, only 13% to 16% of the population had received the chickenpox vaccine. As a result, there were many more children and young people with chickenpox infection; 1-in-3 in the UK, and 1-in-2 in other countries, despite being of the same average age as the German children. Of course, some children in the UK may have had chickenpox prior to being diagnosed with JIA and therefore are no longer at risk.

Why is this important / what is the benefit to patients?

This study found that TB, an infection that clinicians worry about in immunosuppressed people, was extremely rare, which is reassuring. We also showed the benefits of the chickenpox vaccine, demonstrating that it may be useful for those about to start immunomodulatory drugs, particularly as chickenpox in immunosuppressed children and young people can be a very serious disease. In addition, this research has shown that collaborating internationally with other JIA biologic registers means that we have the potential to study rare safety effects in large populations.

Should you wish to read this scientific paper in full, the text can be found online here: https://doi.org/10.1093/rheumatology/keab641

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