Myotonic dystrophy of the 2nd type is caused by expansion of four nucleotides in gene ZNF9 („zinc-finger protein 9“) on the 3rd chromosome. If compared with myotonic dystrophy of the 1st type (19q13.3), it is a variant occurring mainly in Europe and considered to be of lesser frequency. Both types have a number of common clinical features, but also some dissimilarities in the frequency of clinical manifestations. An examination was carried out in a set of patients with clinical and electrophysiological pictures of myotonic myopathy in whom no mutation corresponding with myotonic dystrophy of the 1st type was found out. In the DNA diagnostics, methods of PCR and „Triplet- Primed“ PCR were applied. 18 positive mutations were revealed. The probands’ complaints were manifested between 20 and 50 years of age, on the average, at 33 years. 16 cases presented proximal weakness of the lower extremities, on contrary, one patient showed the shoulder girdle weakness. Out of systemic problems, cataract was present in 9 cases, scoliosis in 2 patients, leukoencephalopathy in 2 subjects. The involvement of a conductive system was found 3x, muscular pains were reported by 8 subjects.

        Key words: type 2 myotonic dystrophy, proximal myotonic myopathy, gene ZNF9, Triplet-Primed PCR