Association between COVID‐19 and myasthenia gravis (MG): A genetic correlation and Mendelian randomization study

BACKGROUND: Observational studies have suggested an association between coronavirus disease 2019 (COVID‐19) and myasthenia gravis (MG). Here, we aimed to estimate the genetic correlation and causal relationship between COVID‐19 susceptibility, hospitalization, severity, and MG phenotypes using linkage disequilibrium score regression (LDSC) and Mendelian randomization (MR) approach. METHODS: Summary statistics of COVID‐19 susceptibility, hospitalization, and severity were used as instrumental variables for exposure traits. Large‐scale genome‐wide association study (GWAS) data for MG were used as outcome traits. The inverse variance weighted approach was used for the main MR analysis, complemented by MR‐Egger, weighted median, simple mode, and weighted mode methods. Sensitivity analysis was implemented using Cochran's Q test, MR‐PRESSO method, and MR‐Egger intercept test. RESULTS: LDSC analysis did not reveal any genetic correlation among COVID‐19 susceptibility, hospitalization, severity, and MG phenotypes, including MG, early‐onset MG, and late‐onset MG (p > .05). Our MR analysis did not provide evidence supporting a causal effect of COVID‐19 susceptibility, hospitalization, or severity on MG phenotypes (p > .05). Extensive sensitivity analysis strengthened the robustness and consistency of the MR estimates. CONCLUSION: Our study did not find evidence of a genetic correlation or causal relationship among COVID‐19 susceptibility, hospitalization, severity, and MG. Future studies with more GWAS data are needed to evaluate the association between COVID‐19 phenotypes and MG and its subgroups.