Abnormal spontaneous electrical activity and gross enlargement of muscle.

In a patient with congenital hypertrophy of the right leg, there developed progressive enlargement of the extremity and inflammatory pseudotumor and electrical myotonia within the enlarged muscle. In three other reported cases, progressive muscle enlargement was associated with abnormal spontaneous electrical and mechanical activity of muscle. In all four cases, the muscle enlargement was probably due to a combination of work hypertrophy secondary to the abnormal mechanical activity and stretch-induced hypertrophy of denervated muscle.