Smooth muscle involvement in congenital myotonic dystrophy.

Dysfunction of smooth muscles is not unusual in adults suffering from myotonic dystrophy but has not yet been reported in patients with the congenital form of the disease. Of two brothers, the younger one presented with the typical features of congenital myotonic dystrophy at birth. He developed severe constipation due to megacolon during his second year of life. In the older brother disturbances of gastrointestinal motility, causing repeated bouts of subileus during the newborn period, sprue-like symptoms during early childhood, and megacolon with constipation and incontinence later on, remained the only manifestation of myotonic dystrophy until the age of eight years when the diagnosis could be finally established by electromyography.