Neuromuscular diseases 2: muscular dystrophies (MD)

Traditionally, muscular dystrophies (MDs) are progressive, hereditary, and primarily degenerative myopathies. Nowadays, due to molecular biology, MDs are looked upon as clinically and genetically heterogeneous myopathies characterized by protein defects of muscle tissue resulting most often in muscle weakness. They are caused by gene mutations leading to a decrease of structural proteins or enzymes. The site of the primary defect and the protein function are different. The disorders are defined according to the underlying protein defect (dystrophinopathy, calpainopathy, and others). The gene or gene product are not yet known in all forms of MD (for example, facioscapulohumeral muscular dystrophy). Therefore, the nomenclature based on the protein defects and the term MD are used concurrently. Clinical symptoms, pathogenesis, diagnosis, therapy, prognosis, and possible prevention of the more frequent MDs are discussed: dystrophinopathies (Duchenne, Becker type), Emery-Dreifuss syndrome (3 forms), facioscapulohumeral MD, limb-girdle MD (17 forms), myotonic dystrophies (2 forms), and congenital MD (11 forms). This article highlights the significance of molecular analyses and the possible multisystemic symptoms in these myopathies.