|Metabolic diseases of muscle can affect all of the body's
voluntary muscles, such as those in the arms, legs and trunk.
Some also can involve increased risk of heart or liver disease,
and the effects can damage the kidneys.| Metabolic diseases of
muscle were first recognized in the second half of the 20th
century. Each of these disorders is caused by a different
genetic defect that impairs the body’s metabolism (the
collection of chemical changes that occur within cells during
normal functioning). Muscles require a lot of energy to work
properly, and metabolic diseases of muscle interfere with
chemical reactions involved in drawing energy from food. When
energy levels become too low, muscle weakness and exercise
intolerance with muscle pain or cramps may occur. In a few
metabolic muscle disorders, symptoms aren’t caused so much by a
lack of energy, but rather by unused fuel molecules that build
up inside muscle cells. This buildup may damage the cells,
leading to chronic weakness. For more, see Types of Meta