MYOM3 (myomesin 3) is a structural protein that links the intermediate filament cytoskeleton to the M-disk of myofibrils in striated muscle 1. It functions as a component of M-band architecture and participates in sarcomere organization and muscle structural integrity 2. MYOM3 is implicated in multiple cardiac pathologies: rare loss-of-function variants in MYOM3 were identified in dilated cardiomyopathy (DCM) patients, with a stop-gained SNV showing association with DCM pathophysiology 3. In heart failure, MYOM3 expression is altered through DNA methylation changes, with hypermethylation associated with downregulation in dilated cardiomyopathy 4. Clinically, MYOM3 fragments circulate in serum and serve as biomarkers for muscle disease monitoring: elevated MYOM3 fragments are present in Duchenne muscular dystrophy and other muscular dystrophies, with levels responding to therapeutic interventions and showing lower variability than creatine kinase 5. Recently, MYOM3 has been identified as a plasma biomarker for distinguishing immune checkpoint inhibitor-related myocarditis from acute myocardial infarction 1, and for detecting retinal vascular involvement in pediatric uveitis through association with coagulation cascade pathways 6. These findings suggest MYOM3 as both a functional cardiac-skeletal protein and a promising diagnostic biomarker for multiple muscle and immune-mediated pathologies.