OBSCN encodes obscurin, a giant cytoskeletal protein essential for muscle fiber structural integrity and function in both cardiac and skeletal muscle 1. The protein serves as a structural constituent of muscle and plays key roles in sarcomere organization, localizing to the M-band, Z disc, and sarcolemma 2. OBSCN functions as a guanyl-nucleotide exchange factor with RhoGEF activity and exhibits protein kinase activity, regulating small GTPase-mediated signal transduction. The gene undergoes extensive alternative splicing during human cardiac and skeletal muscle development, producing tissue-specific isoforms 3. Truncating variants in OBSCN are significantly associated with hypertrophic cardiomyopathy (HCM), with affected patients showing increased risk of cardiovascular death and all-cause mortality 4. OBSCN mutations have been linked to various cardiomyopathies including HCM, dilated cardiomyopathy, and left ventricular non-compaction 25. The protein shows age-related mutation patterns, being a top mutated gene in adult cardiomyopathy patients and enriched for protein-truncating variants 6. Additionally, OBSCN variants have been associated with rhabdomyolysis, demonstrating the protein's critical role in maintaining muscle fiber integrity 1.