Hypertrophic cardiomyopathy (HCM) is a prevalent inherited cardiac condition, affecting approximately 1 in 500 individuals.1 Recent research highlights immune cell involvement in HCM, with altered levels of various immune populations associated with the disease.2 However, whether these changes are causative or merely correlational is still uncertain. This study aims to investigate the causal effects of 731 immune cell types on HCM using comprehensive bidirectional Mendelian randomization (MR), a robust method for assessing causal inference in observational studies.3