The relationship between muscle pathology and DM kinase abnormalities in patients with dystrophia myotonica

We studied the relationship between muscle pathology and the number of trinucleotide (CTG) repeats observed in lymphocytes and biopsied muscle tissues from patients with dystrophia myotonica (DM). The diameter of type 1 muscle fibers was smaller than that of type 2 fibers in all patients. The diameter and proportion of each muscle fiber type were related to the patient's age, but not to the number of trinucleotide (CTG) repeats of DM kinase in biopsied muscles. On the other hand, the proportion of type 1 fibers with central nuclei was closely related to the number of trinucleotide (CTG) repeats in muscles. These findings suggest that DM kinase abnormalities influence the muscle nuclei, and increase the number of central nuclei.