# Causal relationship between primary sclerosing cholangitis and systemic lupus erythematosus: a bidirectional Mendelian randomization study

## TL;DR

This study finds that primary sclerosing cholangitis may increase the risk of developing systemic lupus erythematosus, but not the other way around.

## Contribution

The study provides novel evidence of a causal link from PSC to SLE using bidirectional Mendelian randomization.

## Key findings

- PSC is associated with a 33% increased risk of SLE (OR: 1.33, 95% CI: 1.10–1.61, P=0.0039).
- SLE does not have a significant causal effect on PSC.
- Results were consistent across multiple MR methods and sensitivity analyses.

## Abstract

Observational studies have found a link between two autoimmune diseases, namely, primary sclerosing cholangitis (PSC) and systemic lupus erythematosus (SLE). However, the relationship remains unclear.

Bidirectional Mendelian randomization (MR) analysis and statistical methods, including inverse variance weighting, weighted median, and MR-Egger tests, were performed using data from genome-wide association studies to detect a causal relationship between PSC and SLE. Sensitivity analyses were subsequently performed to assess the robustness of the results. Univariate MR methods were also investigated.

Results of MR analysis suggested that PSC was associated with an increased risk for SLE (odds ratio: 1.33, 95% confidence interval: 1.10–1.61, P=0.0039) However, SLE had no significant causal relationship with PSC.

Results of MR analysis revealed that patients with PSC were at an increased risk for SLE, which provides new insights into the relationship between these two autoimmune diseases.

The online version contains supplementary material available at 10.1186/s40001-024-01941-1.