Molecular bases of autosomal recessive limb-girdle muscular dystrophies

Limb-girdle muscular dystrophies (LGMD) are a heterogeneous group of genetically determined disorders with a primary or predominant involvement of the pelvic or shoulder girdle musculature. The clinical course is characterized by great variability, ranging from severe forms with rapid onset and progression to very mild forms allowing affected people to have fairly normal life spans and activity levels. Sixteen loci have been so far identified, six autosomal dominant and ten autosomal recessive. Linkage analyses indicate that there is further genetic heterogeneity both for dominant as well as for recessive LGMD. The dominant forms (LGMD1) are generally milder and relatively rare, representing less than 10% of all LGMD. The autosomal recessive forms (LGMD2) are much more common, having a cumulative prevalence of 1:15,000 with a number of geographical differences. The product of ten autosomal recessive LGMD genes has so far been identified. They are: calpain-3 (LGMD2A), dysferlin (LGMD2B), alpha-sarcoglycan (LGMD2D), beta-sarcoglycan (LGMD2E), gamma-sarcoglycan (LGMD2C), delta-sarcoglycan (LGMD2F), telethonin (LGMD2G), TRIM32 (LGMD2H), fukutin-related protein (LGMD2I) and titin (LGMD2J). There are, however, at least 25% of families who can be excluded from any known locus. The present review is devoted to outline the present advancements in the molecular bases of autosomal recessive LGMD.