There are many different types of MD, each with somewhat different symptoms. Not all types cause severe disability and many don’t affect life expectancy.

Some of the more common types of MD include:

• Duchenne MD – one of the most common and severe forms, it usually affects boys in early childhood; people with the condition will usually only live into their 20s or 30s
• myotonic dystrophy – a type of MD that can develop at any age; life expectancy isn’t always affected, but people with a severe form of myotonic dystrophy may have shortened lives
• facioscapulohumeral MD – a type of MD that can develop in childhood or adulthood; it progresses slowly and isn’t usually life-threatening
• Becker MD – closely related to Duchenne MD, but it develops later in childhood and is less severe; life expectancy isn’t usually affected as much
• limb-girdle MD – a group of conditions that usually develop in late childhood or early adulthood; some variants can progress quickly and be life-threatening, whereas others develop slowly
• oculopharyngeal MD – a type of MD that doesn’t usually develop until a person is between 50 and 60 years old, and doesn’t tend to affect life expectancy
• Emery-Dreifuss MD – a type of MD that develops in childhood or early adulthood; most people with this condition will live until at least middle age

Read more about the types of MD and diagnosing MD.