Mendelian randomization reveals causal effect of Hashimoto's thyroiditis on immune thrombocytopenic purpura

Patients with immune thrombocytopenic purpura (ITP) usually express thyroid antigen-specific antibodies. The purpose of this study was to explore the causal relationship between Hashimoto's thyroiditis (HT) and ITP.

A two-sample Mendelian randomization (TSMR) analysis was applied to investigate the potential causal relationship between HT and ITP in European population. Five complementary methods including inverse variance weighted (IVW), Mendelian Randomization-Egger (MR-Egger), weighted median, and weighted mode were performed in our study. Risk genes of HT and ITP were selected through Mendelian randomization (MR), and the common risk genes were further analysed by bioinformatics methods to explore the common pathogenesis of the two diseases.

The MR analysis revealed a potential causal relationship between HT and risk of ITP [odds ratio (OR) = 1.22; 95% confidence interval (CI) 1.01, 1.49; P = 0.046]. Gene eQTL data were obtained from the IEU database. HT and ITP were respectively treated as outcome variables for MR analysis, and a total of 32 common risk genes were selected, including 12 high-risk genes and 20 low-risk genes. Functional analysis including Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genome (KEGG) analysis revealed that risk genes were closely related to antigen processing and presentation, and played a crucial role in the process of various viral and bacterial infections.

Our study demonstrated that HT may increase the risk of ITP, and revealed the role of their common risk genes in the development of the two diseases.