Abstract
The authors present their experience with molecular-genetic diagnostics of myotonic dystrophy type 1. The disease is associated with a CTG-triplet expansion in the 3' non-translated region of the myotonin protein kinase gene.
Using an example of a family with two affected members, they demonstrate and compare methods using polymerase chain reaction (PCR), triplet repeat-primed PCR (TP PCR) and restriction fragment length-polymorphism (RFLP). In a four-member family (parents and two daughters) with clinical symptoms of myotonic dystrophy type I in the mother and one of the daughters, the above mentioned methods were used to demonstrate CTG-triplet expansion and to determine the approximate sizes of these expansions.
A considerable increase of the expansion was found in the affected daughter relative to the mother, in agreement with the more severe clinical affection of the daughter, what is a manifestation of the anticipation phenomenon. Furthermore, CTG triplet repeat counts in alleles without expansion were determined in both affected women and in the healthy father and healthy daughter, as well.