Muscular Dystrophy: Hope Through Research: National Institute …

The first historical account of muscular dystrophy appeared in 1830, when Sir Charles Bell wrote an essay about an illness that caused progressive weakness in boys. Six years later, another scientist reported on two brothers who developed generalized weakness, muscle damage, and replacement of damaged muscle tissue with fat and connective tissue. At that time the symptoms were thought to be signs of tuberculosis.

In the 1850s, descriptions of boys who grew progressively weaker, lost the ability to walk, and died at an early age became more prominent in medical journals. In the following decade, French neurologist Guillaume Duchenne gave a comprehensive account of 13 boys with the most common and severe form of the disease (which now carries his nameDuchenne muscular dystrophy). It soon became evident that the disease had more than one form, and that these diseases affected people of either sex and of all ages.

Muscular dystrophy (MD) refers to a group of more than 30 genetic diseases that cause progressive weakness and degeneration of skeletal muscles used during voluntary movement. The word dystrophy is derived from the Greek dys, which means "difficult" or "faulty," and troph, or "nourish." These disorders vary in age of onset, severity, and pattern of affected muscles. All forms of MD grow worse as muscles progressively degenerate and weaken. Many individuals eventually lose the ability to walk.

Some types of MD also affect the heart, gastrointestinal system, endocrine glands, spine, eyes, brain, and other organs. Respiratory and cardiac diseases may occur, and some people may develop a swallowing disorder. MD is not contagious and cannot be brought on by injury or activity.

All of the muscular dystrophies are inherited and involve a mutation in one of the thousands of genes that program proteins critical to muscle integrity. The body's cells don't work properly when a protein is altered or produced in insufficient quantity (or sometimes missing completely). Many cases of MD occur from spontaneous mutations that are not found in the genes of either parent, and this defect can be passed to the next generation.

Genes are like blueprints: they contain coded messages that determine a person's characteristics or traits. They are arranged along 23 rod-like pairs of chromosomes, * with one half of each pair being inherited from each parent. Each half of a chromosome pair is similar to the other, except for one pair, which determines the sex of the individual. Muscular dystrophies can be inherited in three ways:

*Terms in Italics are defined in the glossary.

MD occurs worldwide, affecting all races. Its incidence varies, as some forms are more common than others. Its most common form in children, Duchenne muscular dystrophy, affects approximately 1 in every 3,500 to 6,000 male births each year in the United States.**Some types of MD are more prevalent in certain countries and regions of the world. Many muscular dystrophies are familial, meaning there is some family history of the disease. Duchenne cases often have no prior family history. This is likely due to the large size of the dystrophin gene that is implicated in the disorder, making it a target for spontaneous mutations.

** Centers for Disease Control and Prevention, National Center on Birth Defects and Developmental Disabilities, July 17, 2013

Muscles are made up of thousands of muscle fibers. Each fiber is actually a number of individual cells that have joined together during development and are encased by an outer membrane. Muscle fibers that make up individual muscles are bound together by connective tissue.

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Muscular Dystrophy: Hope Through Research: National Institute ...