The limb-girdle muscular dystrophies: genetic and phenotypic definition of a disputed entity

The past decade witnessed an explosion in our understanding of limb-girdle muscular dystrophy (LGMD). Since Walton and Nattrass1 introduced this term in their classification of the muscular dystrophies, LGMD had been a wastebasket designation. However, with molecular discoveries in the past decade, LGMD has emerged as an entire field within the inherited myopathies; at least five autosomal dominant and ten autosomal recessive gene defects have been identified. Redefined in 1995, the LGMDs are face-sparing, proximally predominant, progressive muscular dystrophies with elevated creatine kinase levels and dystrophic features on muscle biopsy.2 In the current classification system, LGMDs are divided into autosomal dominant (LGMD1) and autosomal recessive (LGMD2) disorders with a superimposed lettering system denoting the chronologic order of chromosomal linkage (thus far, A through E for autosomal dominant and A through J for autosomal recessive LGMDs).3 The table outlines key clinical, laboratory, genetic, and diagnostic features of the 15 LGMD subgroups identified to date. View this table: Table Distinguishing features for diagnosis of the limb-girdle muscular dystrophies Accurate diagnosis is now possible for the majority and is important for genetic counseling. Certain LGMDs are characterized by …