MYOTONIC-DYSTROPHY - MOLECULAR-GENETICS AND DIAGNOSIS

Myotonic dystrophy (DM) is the most common adult muscular dystrophy an d follows an autosomal dominant pattern of inheritance. Up to now, the clinical diagnosis of DM was based on symptoms presented such as ence phalopathy, facies myopathica, paresthesia, atrophy, myotonia, mental retardation, cataract, diabetes, cardiac conduction defects and electr o myography. Since 1991 the specific molecular defect in DM is known a nd a respective diagnosis is possible. The mutation responsible for DM is the expansion of an unstable trinucleotide repeat, (CTG)n, in the 3'-untranslated region of the myotonin protein kinase gene. it is now generally accepted that the CTG repeat length correlates with the clin ical category and the age at onset of the disease; therefore genetic t ests are essential in monitoring and management of DM-patients and the ir family members.Based on the average incidence in Europe about 1000 affected individuals can be expected in Austria, a high percentage of whom is, however, not recognized as carries of the DM-mutation. After having established a genetic diagnosis in Austria allowing the detecti on of this mutation in DM-patients and their relatives, improvement of the diagnostic procedure should be possible.