LRRC18 (leucine-rich repeat containing 18) is a protein involved in immune regulation and disease susceptibility across multiple conditions. The gene functions through protein binding and intracellular signal transduction mechanisms 1. LRRC18 has been identified as a genetic risk locus for systemic lupus erythematosus (SLE) in multiple populations. Genome-wide association studies in Asian populations confirmed LRRC18-WDFY4 as an SLE risk locus, with associations replicated in Caucasian cohorts 1. The nearby WDFY4 gene in this locus is significantly downregulated in SLE patients, regulated through transcription factor Yinyang1 binding 2. LRRC18 has additionally been implicated in inflammatory bowel disease (IBD), particularly ulcerative colitis, as identified through trans-ancestry genome-wide association studies 3. The gene was identified as a key diagnostic marker for coronary artery disease (CAD), showing strong diagnostic efficiency (AUC 0.92-0.96) and correlating with immune cell infiltration patterns including macrophages and T cells 4. LRRC18 expression is significantly altered during high-altitude exposure and has been identified as a potential hub gene for high-altitude polycythemia development 5. While UniProt annotations suggest involvement in spermatogenesis regulation, the provided literature does not support this function.