MYH2 and External ophthalmoplegia: Moreover, autosomal dominant (AD) HIBM with congenital joint contractures and external ophthalmoplegia is associated with a mutation of the Myosin Heavy Chain IIa gene (MyHC-IIa), which causes a pathogenic effect through interfering with filament assembly or functional defects in ATPase activity (Darin et al., 1998; Martinsson et al., 2000).