RT-PCR analysis showed that the ratio of fetal CAPZB exon 8-excluding isoform on total CAPZB transcripts (CAPZBΔ8/CAPZBEx8+CAPZBΔ8) is 48% in DM1, 37% DM2 and 18% in control groups. The gene discussed is CAPZB; the disease is myotonic dystrophy type 1.