What is Myopathy?

The myopathies are neuromuscular disorders in which the primary symptom is muscle weakness due to dysfunction of muscle fiber. Other symptoms of myopathy can include include muscle cramps, stiffness, and spasm. Myopathies can be inherited (such as the muscular dystrophies) or acquired (such as common muscle cramps). Myopathies are grouped as follows:

• Congenital cmyopathies: characterized by developmental delays in motor skills; skeletal and facial abnormalities are occasionally evident at birth
• Muscular dystrophies: characterized by progressive weakness in voluntary muscles; sometimes evident at birth
• Mitochondrial Myopathies: caused by genetic abnormalities in mitochondria, cellular structures that control energy; include Kearns-Sayre syndrome, MELAS and MERRF
• Glycogen storage diseases of muscle: caused by mutations in genes controlling enzymes that metabolize glycogen and glucose (blood sugar); include Pompe's, Andersen's and Cori's diseases
• Myoglobinurias: caused by disorders in the metabolism of a fuel (myoglobin) necessary for muscle work; include McArdle, Tarui, and DiMauro diseases
• Dermatomyositis: an inflammatory myopathy of skin and muscle
• Myositis Ossificans: characterized by bone growing in muscle tissue
• Familial Periodic Paralysis: characterized by episodes of weakness in the arms and legs
• Polymyositis, inclusion body myositis, and related myopathies: inflammatory myopathies of skeletal muscle
• Neuromyotonia: characterized by alternating episodes of twitching and stiffness
• Stiff-man syndrome:  characterized by episodes of rigidity and reflex spasms
• Common muscle cramps and stiffness, and
• Tetany:  characterized by prolonged spasms of the arms and legs