lntroduction:The purpose of this study was to discuss the relation between an expansion of a trinucleotide (CTG) repeat in myotonic dystrophy (DM) and their muscle strength. Subjects 4 families consisted of 8 patients (5 congenital DM and 3 adult onset / carrier DM) were studied. For the normal control, 2 advanced students groups (13 men and 14 women) were included.
Method:To detect an expansion of CTG repeat, polymerase chain reaction (PCR) analysis and non-radioactive Southern blot analysis were performed. For evaluation of muscle strength, occluding strength, grip strength, back strength, isometric extension and flexion strength of the knee, isometric dorsi-and plantar-flexion strength were measured.
Results and discussion:By the Southern blot analysis, fragment include CTG repeat were detected. ln normal control subjects, the number of CTG repeat were under 20 repeat in contrast, in the congenital DM, expanded over 2000 repeat, and in the adult onset / carrier DM, the number of CTG repeat were about 100 - 1500. Grip strength, back strength, plantar-flexion strength tended to decrease in inverse relation to the size of CTG repeat, though, others were not related. Further patients are necessary, successive study will be needed.
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