LGMDR3 is a form of limb-girdle muscular dystrophy, caused due to reduction or absence of the alpha sarcoglycan protein. Like other LGMDs, and especially like other sarcoglycopathies, LGMDR3 is characterized by muscle weakness of the proximal girdle muscles. In LGMDR3, the thigh muscles and muscles of the shoulder blades are the most severely affected. Patients in whom the disorder appears early on in life have a severe form of the disease, whereas those in whom the condition expresses itself later on in life usually have a much milder course of progression.

LGMD2D is caused as a result of mutations in the alpha sarcoglycan gene (SGCA), located on chromosome 17. Alpha sarcoglycan forms the sarcoglycan complex in association with the other sarcoglycan proteins. This complex itself, interacts with other proteins like dystrophins, dystrophin associated glycoproteins, and dystroglycans to form the dystrophin-glycoprotein complex, which in turn functions to bind actin to the extracellular matrix of myocytes.