What causes LGMD2B/Miyoshi?
LGMD2B and Miyoshi are both caused by inherited genetic mutations in the gene for dysferlin. They are recessive conditions, so patients with these diseases must have two defective copies of the dysferlin gene. There are many different mutations that disrupt the function of dysferlin, and each patient usually has different mutations in each of his/her two copies of the gene. People with only one defective gene do not have symptoms. An individual may have genetic defects in the dysferlin gene for the following reasons: • Inheritance of a defective gene from each parents (autosomal recessive inheritance) • Sporadic mutations We do not yet understand why defects in the same gene give rise to both Miyoshi myopathy and LGMD2B, with their slightly different clinical manifestations. In most cases the defect produces some symptoms from both conditions.
