Cause
The cause of myotonic dystrophy is the lengthening of a section in chromosome 19 beyond a certain degree. This leads to a reduced production of a protein that is partly responsible for the stability of the muscle fiber membrane. The extent of elongation increases with inheritance from generation to generation and shows some correlation with the onset and severity of symptoms.
Symptoms
In the adult form of myotonic dystrophy, the combination of progressive muscle weakness, especially in the hand and forearm, foot and facial muscles, with a delayed slackening reaction of the muscles after exercise (myotonia). This can also be observed especially in the hand and finger muscles as well as in the facial and pharyngeal muscles. For example, affected persons report difficulties in loosening a clenched fist or in opening their closed eyes again.
As the disease progresses, it can lead to progressive swallowing difficulties or, by infesting the respiratory muscles, to impaired breathing. Rhythm disturbances are observed in the heart, heart palpitations and stumbling. In the area of the reproductive organs, symptoms such as testicular shrinkage, absence or irregular menstruation and pregnancy complications are observed.
Patients also frequently experience clouding of the lens of the eye (cataract) and inner ear hearing loss. In the infantile form of myotonic dystrophy, the affected children are conspicuous at an early age by muscle weakness (“floppy infant” = flaccid newborn), weakness in drinking and thriving and delayed motor development. The course of the disease is usually more severe. The late course of the disease may be atypical and, for example, may only be discovered in the course of further diagnostic procedures for cataracts or in the course of a family investigation of cases of the disease in direct descendants.Patients with myotonic dystrophy have an increased risk of anaesthesia, since the disease can lead to complications, especially in the cardiovascular and respiratory systems, more often than in healthy patients. Therefore, it is important that the anesthesiologist is informed about the presence of the disease before surgery.
