Not only do they vary between the types, there are variations within each type. The conditions are sometimes obvious at birth, but at other times not until early childhood or later. Some people with myopathies use wheelchairs, others walk with the assistance of braces or other aids, and some appear to have no difficulties with mobility. Yet all have the same problems with their muscles. Children generally progress thoughout childhood, but the course of the disorder is variable in adulthood.
Some people have no apparent problems, while others have decreasing mobility.
Some also have muscle pain. Generally, those least affected as children have the fewest problems as adults, but not always. If it seems I'm qualifying each statement, it's because that's the nature of myopathies. There are general trends, but with exceptions to almost all. There are variants of two types of myopathies which present in a severe infantile form.