Bethlem Myopathy and the Role of the Sarcolemma
Introduction Bethlem myopathy (BM) is a rare, inherited muscular disorder that primarily affects skeletal muscles and connective tissue . It is classified as a mild congenital muscular dystrophy , meaning it causes progressive muscle weakness and joint stiffness (contractures) but is generally less severe than other muscular dystrophies. A key aspect of this disease is the interaction between collagen and the sarcolemma (the muscle cell membrane), which plays a crucial role in muscle function and stability. 1. Causes & Genetics Mutations in Collagen VI Genes Bethlem myopathy is caused by mutations in the COL6A1, COL6A2, or COL6A3 genes , which encode Collagen Type VI . This type of collagen is essential for the stability and function of the extracellular matrix (ECM) , which surrounds muscle fibers and connects them to the sarcolemma . How Collagen VI Mutations Lead to Muscle Weakness Defective Collagen VI production → Weakens the ECM, reducing mechanical support for the s...