1. W. Douglas Biggar, MD* 1. *Professor of Paediatrics, University of Toronto, Bloorview Macmillan Children’s Centre, Toronto, Ontario, Canada After completing this article, readers should be able to: 1. Describe the pathogenesis of Duchenne muscular dystropy (DMD). 2. Describe the natural history and late complications of DMD. 3. List the laboratory investigations available to diagnose muscle disorders. 4. Discuss the management for DMD. MD was born following a normal pregnancy and delivery. His parents were nonconsanguineous, and the family history was unremarkable. He had a 6-year-old brother who was well. MD walked when he was 18 months old, 6 months later than his brother. He was a toe-walker and had large calves. He never ran as well as his brother, and he could not hop on one foot. By 4 years of age, he had difficulty climbing stairs at home and the ladder at the neighborhood playground. His pelvic girdle muscles were weak, he walked with a rocking, side-to-side, waddling gait (Trendelenburg), and he developed lumbar lordosis. He fell more frequently for no apparent reason. His parents became concerned and sought medical advice. Laboratory testing revealed a serum creatine kinase value 50 times greater than normal. On genetic testing, Duchenne muscular dystrophy (DMD) was diagnosed. His weakness progressed. To get up after falling, he would have to use his hands to climb up his legs to stand. In the first grade, his academic performance was judged to be delayed. His teachers noticed that his concentration was poor; he had difficulty staying on task. He scored higher on his verbal intelligence quotient than on his performance intelligence quotient. He also was teased by other children at recess. His parents elected to have him repeat the first grade. He required an educational assistant for classroom activities. He also displayed some obsessive-compulsive behaviors. When he was 10 years old, walking became more difficult, and he required a wheelchair for ambulation. His weight gain became excessive as …