Phosphate esters in myotonic human muscle.

Myotonia congenita is a disorder of the relaxation of skeletal muscle in man. The disease is not accompanied by muscular wasting, and is analogous to a disorder in goats (Kolb, 1938; Brown and Harvey, 1939). The affected muscles both of man and goat show similar abnormalities when examined by histological and electromyographic methods. Myotonia becomes apparent during activity after a period of rest. Relaxation is delayed for up to a minute after the first voluntary contraction. With successive contractions the period of myotonic contraction decreases until the muscle eventually behaves like normal muscle. Electromyographic investigations have suggested that both disorders are due primarily to an abnormally high excitability of the muscle membranes, but it is possible that other factors are operative. Current theories of muscular contraction (Baldwin, 1952) assign an important role to phosphate esters. The patient who is to be described willingly consented to biopsy of small samples of affected muscle to see if they showed abnormalities in the distribution of these esters and thus possibly throw further light on the nature of the disease.