Disease taxonomy--monogenic muscular dystrophy

The field of the autosomal recessive progressive muscular dystrophies has clarified significantly following the recent elucidation of the genetic and molecular etiology of a number of these entities. These studies illustrate how genetics provides a rationale and objective basis for a new, refined nosology. Furthermore, whereas most of these studies point towards the pivotal role played by a number of structural proteins--all directly or indirectly associated with dystrophin--a calpain protease was shown to be involved in the Reunion-type limb girdle muscular dystrophy. This discovery raises the issue of whether these mechanisms are all part of one and the same pathway or of distinct pathophysiological pathways (structuropathy versus enzymopathy) leading to similar phenotypes. Finally, all of these diseases are considered as classical monogenic traits. Some findings suggest, however, that epistatic interactions have been overlooked and that the inheritance models could be slightly more complex. These results are discussed in light of the coming challenges of the identification of genes underlying complex multifactorial traits