What are the genetic changes related to limb-girdle muscular dystrophy ?
The various forms of limb-girdle muscular dystrophy are caused by mutations in many different genes. These genes provide instructions for making proteins that are involved in muscle maintenance and repair.  Some of the proteins produced from these genes assemble with other proteins into larger protein complexes. These complexes maintain the physical integrity of muscle tissue and allow the muscles to contract. Other proteins participate in cell signaling, cell membrane repair, or the removal of potentially toxic wastes from muscle cells.  Limb-girdle muscular dystrophy is classified based on its inheritance pattern and genetic cause. Limb-girdle muscular dystrophy type 1 includes forms of the disorder that have an inheritance pattern called autosomal dominant. Mutations in the LMNA gene cause limb-girdle muscular dystrophy type 1B. Limb-girdle muscular dystrophy type 1C is one of a group of muscle disorders called caveolinopathies caused by mutations in the CAV3 gene.  Limb-girdle muscular dystrophy type 2 includes forms of the disorder that have an inheritance pattern called autosomal recessive. Calpainopathy, or limb-girdle muscular dystrophy type 2A, is caused by mutations in the CAPN3 gene. Type 2A is the most common form of limb-girdle muscular dystrophy, accounting for about 30 percent of cases. Dysferlinopathy, also called limb-girdle muscular dystrophy type 2B, is caused by mutations in the DYSF gene.  Sarcoglycanopathies are forms of limb-girdle muscular dystrophy caused by mutations in the SGCA, SGCB, SGCG, and SGCD genes. These sarcoglycanopathies are known as limb-girdle muscular dystrophy types 2D, 2E, 2C, and 2F respectively.  A TTN gene mutation causes limb-girdle muscular dystrophy type 2J, which has been identified only in the Finnish population. Mutations in the ANO5 gene cause limb-girdle muscular dystrophy type 2L. Mutations in several other genes cause forms of limb-girdle muscular dystrophy called dystroglycanopathies, including limb-girdle muscular dystrophy types 2I, 2K, 2M, and 2N.  Other rare forms of limb-girdle muscular dystrophy are caused by mutations in several other genes, some of which have not been identified.