Muscle filaminopathy

Muscle filaminopathy (also known as filamin C-related myofibrillar myopathy or myofibrillar myopathy type 5, MFM5) is a rare inherited muscular disorder caused by mutations in the FLNC gene, which encodes filamin C, a protein essential for maintaining the structural integrity of muscle fibers. Filamin C plays a critical role in cross-linking actin filaments and anchoring them to the sarcolemma in skeletal and cardiac muscle. When this protein is defective, abnormal protein aggregates accumulate within muscle fibers, leading to progressive muscle weakness and degeneration. The disease primarily affects the skeletal muscular system, typically presenting in adulthood with slowly progressive proximal and distal limb weakness. Patients often first notice difficulty walking, climbing stairs, or performing tasks requiring hand grip strength. A characteristic feature is the presence of myofibrillar disorganization and protein aggregates on muscle biopsy. Cardiac involvement, including restrictive or dilated cardiomyopathy and cardiac conduction defects, can occur and may represent a significant source of morbidity. Respiratory insufficiency may develop as the disease progresses. Serum creatine kinase levels are usually mildly to moderately elevated. There is currently no cure or disease-specific treatment for muscle filaminopathy. Management is supportive and multidisciplinary, focusing on physical therapy to maintain mobility, cardiac monitoring and treatment of cardiomyopathy or arrhythmias, respiratory support when needed, and orthopedic interventions as appropriate. Genetic counseling is recommended for affected individuals and their families. Research into potential targeted therapies is ongoing but remains in early stages.

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