Congenital myotonic dystrophy. Changes in muscle pathology with ageing

Undifferentiated type 2C fibers and satellite cells were increased in number in younger patients with congenital myotonic dystrophy (CMD) indicating immaturity in muscle fiber growth. The changes found in a 38-year-old man with CMD were identical to those described in late onset myotonic dystrophy. Type 1 fibers were found to become predominant with age. This suggests that in this disorder fiber type transformation progresses with age, presumably due to abnormal neural influences or aberrant sarcolemmal responses.