Definition - one of a group of diseases that cause problems with the tone and contraction of skeletal muscles

Cause - mutations in a gene that carries instructions for a sodium channel, a pore in the muscle cell surface that regulates the movement of sodium molecules; or in a gene for a chloride channel, a pore in the muscle cell surface that regulates the movement of chloride molecules

Onset - episodes of prolonged muscle contraction (inability to relax muscles at will) begin in infancy; episodes of weakness generally begin in adolescence, if they occur at all

Symptoms - episodes of prolonged muscle contraction and/or weakness, mostly in face, neck and upper extremities; prolonged contractions sensitive to exercise and cold

Progression - does not progress

Inheritance - autosomal dominant, or produced by a defective gene contributed by one parent

Facts About Myopathies