BAG3-related myofibrillar myopathy

Definition

A rare myofibrillar myopathy characterized by childhood-/adolescent-onset progressive myopathy with proximal and/or distal muscle weakness that commonly progress to involve axial muscles due to BAG3 mutations. Patients present with toe-walking, gait disturbance, fatigue, rigid spine, scoliosis and joint contractures (particularly of the knees, ankles, and hips). Respiratory insufficiency and cardiomyopathy are frequently present. All patients exhibit a sensorimotor axonal/demyelinating (often with giant axons) peripheral neuropathy contributing to distal weakness and sensory loss. Disease typically progress rapidly in childhood-/adolescent-onset patient, however few adult-onset patients reported to have milder, slower progression with limited cardiac or respiratory involvement.