MSH: An inherited congenital myopathic condition characterized by weakness and hypotonia in infancy and delayed motor development. Muscle biopsy reveals a condensation of myofibrils and myofibrillar material in the central portion of each muscle fiber. (Adams et al., Principles of Neurology, 6th ed, p1452),NCI: An autosomal dominant congenital disorder affecting the skeletal muscles. Microscopically, it is characterized by disorganized areas, which are called cores, seen usually in the center of the muscle fibers. Clinically it presents as mild to severe muscle weakness. It may be associated with skeletal abnormalities including scoliosis, joint deformities, and hip dislocation.