RFLNB (refilin B) is a filamin-binding protein that regulates perinuclear actin network organization and nuclear morphology. It interacts directly with filamin proteins to modulate actin filament bundle dynamics and is essential for cartilaginous skeletal development 1. RFLNB functions as a partner molecule of filamin B (FLNB) in regulating chondrocyte differentiation and proliferation, with loss of RFLNB leading to reduced cartilaginous cell numbers, impaired bone growth, and skeletal malformations including spinal curvatures and vertebral fusions 1. At the molecular level, RFLNB facilitates interaction between FLNB and Smad3, which regulates Runx2 expression in developing chondrocytes 1. Beyond skeletal development, emerging evidence suggests RFLNB has broader disease relevance. It is upregulated in inflammation-associated fibroblasts that accumulate in creeping fat of Crohn's disease patients 2, and is included in prognostic gene signatures for metastatic renal cell carcinoma 3, sarcoma 4, and gastric adenocarcinoma 5, where elevated expression correlates with poor prognostic outcomes. RFLNB shows reduced expression in early-onset severe preeclampsia 6. These findings establish RFLNB as a multifunctional regulator with critical roles in skeletal development and potential involvement in tumor progression and inflammatory diseases.