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Myotonia Congenita (MC)
(Thomsen's and Becker's Disease)
Definition - one of a group of diseases that
cause problems with the tone and contraction of skeletal muscles; there are two
types, Becker and Thomsen; Becker is most common
Cause - mutations in a gene that carries instructions for a chloride
channel, a pore in the muscle cell surface that regulates the movement of
chloride molecules
Onset - early to late childhood
Symptoms - delayed muscle relaxation and muscle stiffness, typically
provoked by sudden movements after rest
Progression - does not progress
Inheritance - Becker: autosomal recessive, or produced by defective genes
contributed by both parents; Thomsen: autosomal dominant, or produced by a
defective gene contributed by one parent
