FAM13B (family with sequence similarity 13 member B) is a gene located on chromosome 5-q22 with GTPase activator activity involved in regulating small GTPase-mediated signal transduction 1. A circular RNA derived from FAM13B (circFAM13B) localizes to the endoplasmic reticulum and functions as a tumor suppressor in nasopharyngeal carcinoma by binding to RBM3 protein and promoting degradation of uXBP1 mRNA, thereby inhibiting ER stress-related pathways and lymphangiogenesis 2. In lung adenocarcinoma, FAM13B expression is downregulated and positively correlates with gefitinib sensitivity and immune response, suggesting a role in drug response and immune regulation 3. Additionally, FAM13B expression is altered in peripheral vascular smooth muscle cells under calcifying conditions associated with critical limb ischemia 4. Genome-wide association studies have linked FAM13B to atrial fibrillation susceptibility through cis-expression quantitative trait loci regulation 1. These findings indicate FAM13B participates in ER stress regulation, vascular biology, and immune responses, with potential therapeutic applications in cancer metastasis, drug sensitivity prediction, and cardiovascular disease.