1. Elke H. Roland, MD* 1. 2. *Associate Professor, Division of Neurology, Department of Pediatrics, University of British Columbia; Director, Neuromuscular Diseases Clinic, British Columbia’s Children’s Hospital, Vancouver, British Columbia, Canada. After completing this article, readers should be able to: 1. Explain the inheritance pattern of Duchenne muscular dystrophy and congenital myotonic dystrophy. 2. Describe the primary signs of Duchenne dystrophy. 3. Describe the common clinical features of Duchenne dystrophy, myotonic dystrophy, and congenital muscular dystrophy. 4. Delineate the clinical course of Becker muscular dystrophy, facioscapulohumeral dystrophy, and congenital muscular dystrophy. The term “muscular dystrophy” refers to a group of genetically determined disorders characterized by progressive degeneration of skeletal muscle without primary structural abnormality in the lower motor neuron. These disorders have been classified on the basis of the clinical distribution and severity of muscle weakness and by pattern of inheritance. The majority of muscular dystrophies are associated with progressive muscle weakness and atrophy and elevated concentrations of serum creatine kinase (CK), but these are not absolute findings. Some of the milder varieties, such as facioscapulohumeral dystrophy, may appear relatively static, and patients who have congenital muscular dystrophy even may show functional improvement. Most of the muscular dystrophies have marked, albeit nonspecific, structural abnormalities in muscle biopsies, such as loss (necrosis) of muscle fibers and increased connective tissue (endomysial fibrosis). It is possible that the identification of specific muscle protein abnormalities will lead to a reclassification of the muscular dystrophies. The findings of weakness and elevated CK concentration are common to other disorders of the lower motor neuron, including anterior horn cell disease, peripheral neuropathies, and other metabolic and nonprogressive myopathic conditions. Motor dysfunction of central origin usually presents with hypotonia rather than actual weakness. The overall incidence of muscular dystrophy varies because this term encompasses disorders that have different inheritance patterns. Duchenne/Becker dystrophy is the most common type of muscular dystrophy to present in childhood. Its incidence, based on population studies and neonatal screening programs, is approximately 1 in 3,500 male births. In addition, …