BAG3-related myofibrillar myopathy

BAG3-related myofibrillar myopathy (also known as myofibrillar myopathy type 6, MFM6) is a rare inherited muscle disorder caused by mutations in the BAG3 gene, which encodes a co-chaperone protein essential for maintaining the structural integrity of muscle cells. BAG3 plays a critical role in protein quality control within muscle fibers, and when it is dysfunctional, misfolded proteins accumulate and form abnormal aggregates within muscle cells, leading to progressive muscle weakness and degeneration. The disease primarily affects skeletal muscle and the heart. Patients typically present in childhood or adolescence with progressive limb-girdle or generalized muscle weakness, often accompanied by severe restrictive or dilated cardiomyopathy. Peripheral neuropathy is also a common feature. Respiratory insufficiency may develop as the disease progresses. Muscle biopsy characteristically shows myofibrillar disorganization and accumulation of protein aggregates. The cardiac involvement is often the most life-threatening aspect, and heart failure can develop at a young age. There is currently no cure or disease-specific treatment for BAG3-related myofibrillar myopathy. Management is supportive and multidisciplinary, focusing on cardiac monitoring and treatment of cardiomyopathy (including medications, implantable defibrillators, or heart transplantation in severe cases), physical therapy to maintain mobility, respiratory support when needed, and orthopedic interventions. Genetic counseling is recommended for affected families. The prognosis varies but can be severe, particularly when significant cardiac involvement is present, with some patients requiring heart transplantation in childhood or early adulthood.

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