LMOD3 (leiomodin 3) is essential for organizing sarcomeric actin thin filaments in skeletal muscle, functioning as a key regulator of muscle contractility. Mechanistically, LMOD3 increases the rate of actin polymerization and binds to tropomyosin and nebulin, proteins critical for thin filament stability 1. KLHL40 stabilizes LMOD3 protein levels and blocks its ubiquitination, preventing degradation 2. Loss of LMOD3 function causes nemaline myopathy type 10 (NEM10), a congenital myopathy characterized by muscle weakness, hypotonia, respiratory insufficiency, and joint contractures 3. Disease severity correlates with mutation type: truncating variants cause severe presentations with early onset and respiratory dependence 4, while missense mutations result in milder phenotypes with prominent facial weakness 3. Distinctive rod-like or ovoid nemaline bodies derived from Z-disc material serve as pathological hallmarks of LMOD3-associated disease 1. Beyond skeletal muscle disease, rare LMOD3 variants have been associated with Kleine-Levin syndrome, a periodic hypersomnia disorder, suggesting LMOD3 may play broader developmental roles in brain structures regulating sleep-wake states 5. Notably, LMOD3 mutations account for approximately 21% of arthrogryposis multiplex congenita cases involving skeletal muscle pathology 6.