A congenital myopathy of the musculoskeletal system that covers a wide spectrum of phenotypes and is caused by pathogenic variants in the skeletal muscle beta-Tropomyosin gene. These variants lead to a variety of overlapping adult onset and congenital myopathies characterized by muscle weakness, amyotrophy, hypotonia, myopathic facies, scoliosis, and sometimes contractures among other phenotypes. Histologic findings on skeletal muscle biopsy are variable with nemaline and intranuclear bodies, cap-like lesions, core-like lesions, fiber-type disproportion, and dystrophic features all observed to some degree.