Causal inference between serum bilirubin levels and juvenile idiopathic arthritis-associated uveitis: A bidirectional Mendelian randomization study

Background

Several observational studies have suggested an association between low serum bilirubin levels and Behçet's disease uveitis. However, the causal inference between bilirubin level and juvenile idiopathic arthritis-associated uveitis (JIAU) remains ambiguous. We investigated the potential causal relationship between serum bilirubin levels and JIAU using a bidirectional two-sample Mendelian randomization (MR) framework.

Methods

We systemically integrated summary-level data from published large-scale genome-wide association studies on bilirubin level and JIAU in a Caucasian British population. To determine the causal effect of bilirubin level on JIAU, we constructed strong instrumental variables using 47 and 80 single-nucleotide polymorphisms (SNPs) specific to direct bilirubin and total bilirubin levels, respectively. For reverse causal inference, seven SNPs associated with JIAU were included in our study. Multiple complementary methods were further performed to evaluate the robustness of MR estimates.

Results

The inverse-variance weighted estimate did not show any significant causal associations of genetically predicted serum direct or total bilirubin level with the risk of JIAU (odds ratio [OR]: 1.010, 95% confidence interval [CI]: 0.750-1.359, p = 0.947; OR: 0.867, 95% CI: 0.688-1.093; p = 0.227, respectively). MR-Egger and weighted median methods also obtained similar associations. Additionally, the results of reverse MR analyses using JIAU as exposure showed no associations of genetically predicted risk of JIAU with serum bilirubin levels (p > 0.05). In sensitivity analysis, the causal estimate between serum bilirubin levels and JIAU did not differ when SNPs associated with possible confounders were omitted.

Conclusion

Genetic evidence from our bidirectional analysis did not support a causal association between serum bilirubin levels and JIAU risk in the Caucasian British population. Future large-scale studies should be conducted to validate these findings and explore any causal effects on the disease process.

Reactivation of juvenile idiopathic arthritis associated uveitis with posterior segment manifestations following anti-SARS-CoV-2 vaccination

Background/purpose

Juvenile idiopathic arthritis (JIA) is the most common rheumatic disease in the pediatric population and anterior uveitis is its commonest extra-articular manifestation. Typically the uveitis presents as chronic anterior uveitis and there is limited literature of the posterior segment manifestations of the disease. Similar to other vaccines, anti-SARS-CoV-2 vaccination that began as an urgent measure to control the spread of the SARS-CoV-2 pandemic has not been without adverse events. We are reporting a 19-year-old Asian Indian female who was diagnosed and treated for JIA associated anterior uveitis that was unilateral and was under anti-inflammatory control but showed worsening of uveitis with posterior segment inflammation in both eyes following anti-SARS-CoV-2 vaccination.

Case report

A 19-year-old Asian Indian female with a history of juvenile idiopathic arthritis on treatment with methotrexate, presented with right eye chronic anterior uveitis with peripheral subclinical retinal vasculitis and macular edema which was brought under control following administration of adalimumab. She was inflammation free for 6 months until she received anti-SARS-CoV-2 vaccination and developed new onset floaters in both eyes that were initially noted after the first dose and increased after the second dose. Clinical examination revealed presence of keratic precipitates and grade 1+ anterior chamber inflammation along with vitiritis in both eyes. Fundus fluorescein angiography revealed angiographically active retinal vasculitis without the presence of macular edema in both eyes. This was managed with a short course of topical difluprednate and continuation of systemic immunosuppressive therapy with adalimumab and methotrexate.

Conclusion

JIA associated uveitis results from an autoimmune process which can be controlled with timely immunosuppressive treatment. It is important to be aware of the potential risk of flare up of uveitis with posterior segment manifestations following anti- SARS-CoV-2 vaccination.