The limb-girdle muscular dystrophies-multiple genes, multiple mechanisms.

In the field of muscular dystrophy, advances in understanding the molecular basis of the various disorders in this group have been rapidly translated into readily applicable diagnostic tests, allowing the provision of more accurate prognostic and genetic counselling. The limb-girdle muscular dystrophies (LGMD) have recently undergone a major reclassification according to their genetic basis. Currently 13 different types can be recognized. Amongst this group, increasing diversity of the mechanisms involved in producing a muscular dystrophy phenotype is emerging. Recent insights into the involvement of the dystrophin glycoprotein complex in muscular dystrophy suggests that its members may play distinct or even multiple roles in the maintenance of muscle fibre integrity. In other forms of LGMD, proteins have been implicated which may be important in intracellular signalling, vesicle trafficking or the control of transcription. As these various mechanisms are more fully elucidated, further insights will be gained into the pathophysiology of muscular dystrophy. At a practical level, despite the marked heterogeneity of this group real progress can at last be made in determining a precise diagnosis.